Which sentence contains a singular subject? both jerry and his sister attended the meeting. several in the audience gave the actors a standing ovation. the deer entered the forest at the same place they had come out. any of those ideas sounds good to me.

(1) Both Jerry and his sisterthis is plural because it is more then 1.
(2) Several ...talking about more then 1so its plural
(3) The deerthis could be singular or plural...however, when u read further, it later says " the same place THEY had come outso it is plural.
(4) Any (of those ideas)Any (ONE) of those ideassingular

The bell is just a signal that the set time of the end of class is passing. the teacher lets you know when it's okay to leave.