<p>It is asking for bond angles between the NH bonds. NH2- has a bent shape with 2 lone pairs, causing the H's to bunch up and have a low angle between each other.</p>
<p>NH3 has a single lone pair, so it is trigonal pyramidal which bunches up the H's. </p>
<p>NH4 has no lone pairs and is tetrahedral so the H's are evenly spaced.</p>
<p>Remember that the high concentration of negative charge around lone pairs causes them to repel other bonded pairs. I'm not sure if this makes much sense as I am having doubts myself as to WHY lone pairs repel bonded pairs more than lone pairs.</p>