Marco Has Been Running Each Afternoon Trying to Beat His

Marco has been running each afternoon trying to beat his college's record for the 400-metre sprint.Despite all his practising,he hasn't been able to come in under his usual time.There's a big fan turnout for the track meet on Saturday against the rival school and Marco not only beats the old record,but far surpasses it.Marco's behaviour illustrates

A) social facilitation.
B) social compensation.
C) social loafing.
D) the bystander effect.