Advanced American English Quiz; Lesson 3; Part 3

Level up your English from basic to intermediate and advanced.
American English Quiz, Lesson 3. Part 3.
Which group includes unrelated words?
hone in on, adjust direction or focus precisely
subdued, muted, toned down, restrained
backfire, opposite result, contrary to intended purpose
chronic muscle tension, missile, compromise, custody

Which group explains “put your foot down”?
assert authority, end debate or resistance, enforce bound, firmness
back to back, continuously, backs touching, consecutive
swatch, sample, representative, small portion or example
tissue, stitched together, vivid portrait, exhaust system