I have been authoring rather lengthy multi step problems for high school physics. I have had a great deal of success with getting questions with units to work but is I try and include a multiple choice type question in the sequence the result for submission suggests that the answer chosen from the pull down menu needs units. I was hoping some one could help me figure this out. Also sorry about the super long code

I am rather new to authoring problems and I have learned from looking at examples of code so. . . . Here is the code for the problem I am working with

# DESCRIPTION## WeBWorK problem written by Justin Heckman# Council Bluffs Community Schools# ENDDESCRIPTION## DBsubject('')## DBchapter('')## DBsection('')## KEYWORDS('')## TitleText1('')## EditionText1('')## AuthorText1('')## Section1('')## Problem1('')## Author('Justin Heckman')## Institution('Council Bluffs Community School District')DOCUMENT();loadMacros("PGbasicmacros.pl","PGstandard.pl","PGcourse.pl","MathObjects.pl","PGauxiliaryFunctions.pl","PGchoicemacros.pl","PGanswermacros.pl",,"answerHints.pl","scaffold.pl","parserNumberWithUnits.pl","parserFormulaWithUnits.pl","PGML.pl","parserPopUp.pl");######################################################################################Context("Numeric");$xh= random(10, 30, 2);$vb= random(5, 15 , 1);$vobu= NumberWithUnits("0 m/s");$g=(9.81);$ag= NumberWithUnits("9.81 m/s^2");$xhu= NumberWithUnits("$xh m");$t= (sqrt(2*$xh/$g));$tu= NumberWithUnits("$t s");$xb= ($vb*$t);$xbu= NumberWithUnits("$xb m");$xhgg= random(150, 200, 2);$vC= random(20, 30, 1);$tbgg= (sqrt(2*$xhgg/$g));$xC= ($vC*$tbgg);$ns= ($xC/4);$nsu= NumberWithUnits("$ns m");$popup = PopUp(["?","a","b","c"],"c",);###################################################TEXT(beginproblem());###################################################BEGIN_PGMLThe subject of the 16 bit game Water Balloon Drop was to drop waterballoons from the top of buildings on unsuspecting bystanders. While thegame was rather lame a lacked dimension it does make for a good physicsproblem. By examining the height of the characters in the game in comparisonto the height that the balloons were dropped,it can be determined that theballoons are being dropped from a height of [$xh] m . Considering thatcyclists are worth more points and that they travel at a rate of [$vb] m/s on averagewe can use the following to determine how much ahead of a cyclist a balloonmust be dropped to strike a cyclist.a.) To find the answer to the posed question we will need to determine the the time it take forthe balloon to fall to the ground. To do so we will need to fill out a [:vvaxt:]. By examining thescenario we can determine the initial velocity of the water balloon, what is it?[_____]{$vobu}.b.) Since the building is on earth we can also determine the rate at which the balloon speedsup as it fell, a value we refer to as the acceleration due to gravity. What is theacceleration?[_____]{-$ag}.c.) Finally, we know the distance (x) that the balloon will fall, enter it now![_____]{$xhu}.d.) Now that we have 3 pieces of information in our vvaxt we can now determine theremaining pieces. Since we really want to know how far thebike will travel in the time it takes for the balloon to fall whatwe need to calculate is the time (t) that it takes the balloon tofall to the ground. Which formula will you use to solve fortime?A.) [: V_f=v_o+at :]B.) [:v_f^2=v_o^2+2ax:]C.) [:x=v_o*t = (1/2*a*t^2):][@ $popup->menu() @]*e.) How long will it take the balloon to fall to the ground?[_____]{$tu}.f.) Considering that the cyclist travels at 6 m/s how far in front of the moving cyclist should theballoon be dropped?[_____]{$xbu}.g.) The subject of a totally different but similargame is to drop water balloons from the top of thegolden gate bridge tower on top of passing cars.The towers have a height of [$xhgg] meters, accordingto Google, and that cars drive an average of [$vC] m/sacross the bridge. In this game we will assume thatthe beginning of each white stripe is 4 m from thebeginning of the next (2m stripe and 2m gap). If thisis game how many white stripes away from the edgeof the beam should a car be when the balloon is released in order to strike a car traveling ataverage speed?[_____]{$nsu}.END_PGMLinstall_problem_grader(~~&std_problem_grader);$showPartialCorrectAnswers = 0;ANS( $popup->cmp() );####################################################ENDDOCUMENT();