Answer: Choice D
If the coach puts Tara and Laney on Team B, the mean height of the players on Team B will be shorter than 5 feet 10 inches
We know that Tara is 5 feet 9 inches. This is shorter than the mean height of team B (which is 5 feet 10 inches). Laney is some height shorter than Tara. While we don't know Laney's exact height, we know that her being shorter than 5 foot 9 inches means that the mean height will be pulled down. Tara being shorter than 5'10" means the mean goes down as well. Both new players pull the average down to a shorter height. That exact new mean isn't something we can determine as there isn't enough information; however we know in general the mean will decrease. This only works with Team B since both players are shorter than the mean here. Team A won't work because Tara is taller than the average height for this team, and its not clear where Laney's height ranks with team A.