Question: Gridlines in plots in Maple TA

Hi there,

How can I get gridlines in my plots in Maple TA? Se eg. the source of the following question:

Thanks alot in advance!

mode=Multiple Choice@
name=Grafen for den afledede@
comment=@
editing=useHTML@
solution=@
algorithm=$r = rint(3);
$f1 = rint(3);
$f2 = rint(3);
condition: ne($r,$f1);
condition: ne($r,$f2);
condition: ne($f1,$f2);
$rf = switch($r,x^2,cos(x),x);
$ff1 = switch($f1,x^2,cos(x),x);
$ff2 = switch($f2,x^2,cos(x),x);
$fm = mathml("$rf");
$opgaveplot = plotmaple("plot($rf,x=-10..10), plotdevice='gif', plotoptions='height=250,
width=250'");
$rplot=plotmaple("plot(diff($rf,x),x=-10..10), plotdevice='gif', plotoptions='height=250,
width=250'");
$fplot1=plotmaple("plot(diff($ff1,x),x=-10..10), plotdevice='gif', plotoptions='height=250,
width=250'");
$fplot2=plotmaple("plot(diff($ff2,x),x=-10..10), plotdevice='gif', plotoptions='height=250,
width=250'");@
uid=61d45fb9-b1cc-4e0b-a986-9bbb24985734@
privacy=10@
allowRepublish=false@
description=@
difficulty=0.0@
modifiedBy=669aa1fb-4bde-408c-ae4d-6fa47454164c@
school=d1f34b37-d475-429f-b82f-5a0479c33756@
attributeAuthor=true@
numberOfAttempts=1@
numberOfAttemptsLeft=1@
numberOfTryAnother=0@
numberOfTryAnotherLeft=0@
question=<p>
Betragt funktion f(x) = $fm og dens graf herunder.&nbsp;</p>
<p style="text-align: center; ">
$opgaveplot</p>
<p style="text-align: center; ">
&nbsp;</p>
<p>
Angiv hvilken af følgende figurer repræsenterer grafen for funktionen?</p>
@
answer=1@
choice.1=$rplot@
choice.2=$fplot1@
choice.3=$fplot2@
choice.4=Ingen af dem@
choice.5=Der er flere rigtige@
fixed=@