For each of the following pairs of statements, use Modus Ponens or Modus Tollens to fill in the blank line so that a valid argument is presented.
(a) If Janice has trouble starting her car, then her daughter Angela will check Janice's spark plugs.
∴ Janice had trouble starting her car.
(b) If Brady solved the first problem correctly, then the answer he obtained is 137.
Brady's answer to the first problem is not 137.
(c) If this is a repeat-until loop, then the body of this loop is executed at least once.
∴ The body of the loop is executed at least once.
(d) If Tim plays basketball in the afternoon, then he will not watch television in the evening. ∴ Tim didn't play basketball in the afternoon.