Which is the most likely error in scientific hypothesis testing?

Which is the most likely error in scientific hypothesis testing?
 
  a. confirmation bias
  b. modus ponens
  c. modus tollens
  d. anchoring and adjustment heuristic

Question 2

Consider this problem. What does it represent? If it is a weekend, Mark is sailing. Mark is sailing. Thus, it is a weekend.
 
  a. valid syllogistic reasoning problem
  b. invalid syllogistic reasoning problem
  c. valid conditional reasoning problem
  d. invalid conditional reasoning problem

Question 3

Consider this problem. What does it represent? Premise 1: If it is a weekend, Mark is sailing. Premise 2: Mark is sailing. Conclusion: It is a weekend.
 
  a. syllogistic reasoning
  b. affirm the antecedent
  c. illicit conversion
  d. deny the antecedent