A bell ring is the signal
Answer : B. some of the police force
Among the choices above, it is the phrase in letter b wherein the pronoun "some" refers to a single noun which is " the police force". As you can see, the police force refers to a group of policemen making it a collective noun taking the singular form of the verb. The other objects of the pronoun "some" in the other options are all in plural form such as economy cars, native people, and the 6y foods.
The answer to your question is A. - Them because you are referring to the crumbs and just not something random, in which case you would use "it".
I hope this helps you!
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