10 points urgent

i began to get pretty thoroughly ashamed of him for his childishness; and at last, when he repeated that imploring question still another time, i lost my patience for the moment, and spoke pretty brutally to him. it seemed to shrivel him up and cow him; and he looked so wounded and so humble after that, that i detested myself for having done the cruel and unnecessary thing.

what is the meaning of cow as it is used in the sentence?

a. deter

b. disgust

c. frighten

d. dishearten