What is the answerer: which word could best replace the underlined phrase as it is used in the paragraph?

when our scout troops went on the field trip, one of the buses broke down. so our troops were packed like sardines onto the other bus. at first we complained about it being hot and stuffy. but as soon as the windows were open and we started singing, we forgot about the problem.

a.
treated

b.
crowded

c.
slipped

d.
loaded