Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Q: Problem: if each participant of a chess tournament plays exactly one game with each of the remaining participants, then 276 games will be played during the tournament. find the number of participants.
Options: a. 20, b. 22, c. 24, d. 26, e. 28

A: c
****
Q: Problem: of the 20 members of a kitchen crew, 17 can use the meat - cutting machine, 18 can use the bread - slicing machine, and 15 can use both machines. if one member is chosen at random, what is the probability that the member chosen will be someone who can not use either machine ?
Options: a. 0, b. 1 / 10, c. 1 / 7, d. 1 / 4, e. 1 / 3

A: a
****
Q: Problem: a train covers a distance of 12 km in 10 minutes. if it takes 8 seconds to pass a telegraph post, then the length of the train is
Options: a. 100 m, b. 120 m, c. 140 m, d. 160 m, e. 170 cm

A:
d
****