Suppose That I Conduct an Experiment on the Effects of Flattery

Multiple Choice

Suppose that I conduct an experiment on the effects of flattery on compliance.I bring women into the laboratory,tell them they are beautiful,and ask them to lend me $10.I bring men into the laboratory,I don't flatter them,and I ask them to lend me $10.Sure enough,more women than men lend me $10.My conclusion that flattery increases compliance is suspect because

A) I failed to randomly select the sample from the population.
B) my experiment lacks external validity.
C) my experiment lacks internal validity.
D) I have not operationally defined my variables.
E) my experiment lacks generalizability.