Interested in the Effects of Different Kinds of Instruction on Video

Interested in the effects of different kinds of instruction on video game performance, Martin asks 30 college freshmen to each play one hour of Ratchet and Klank.Participants are randomly assigned to one of three instruction groups: (1) complete the tasks as quickly as possible, (2) conserve as much health as possible find gold bolts (worth lots of money in equipment and ammunition) .If Martin averages the scores for each instruction group and then compares them, any differences in the means of the instruction groups reflect:

A) individual differences in hand-eye coordination.
B) inherent differences in the ability of the college freshmen to play video games.
C) within-groups variance.
D) between-groups variance.