Which one of the following questions is concerned with construct validity?

Which one of the following questions is concerned with construct validity?
 
  a. Do the results support the researcher's hypothesis?
  b. Do the results support the theory behind the research?
  c. Are there alternative variables that can be ruled out as potential causes of the behavior or interest?
  d. Are the measuring instruments free of error?

Question 2

When subjects are selected because of the presence or absence of a condition, rather than having a condition assigned to them, the experimenter is testing
 
  a. subject variables
  b. construct validity
  c. face validity
  d. confounding variables

Question 3

A researcher that is exploring gender differences is testing
 
  a. construct validity
  b. subject variables
  c. outliers
  d. confounding variables

Question 4

The threat of confounding is particularly serious in research using
 
  a. randomization
  b. true experiments
  c. subject variables
  d. assignment of subjects to conditions