Prepositional phrase: then the girls had a discussion about safety rules. a) what kind of discussion b) when the discussion took place c) where the discussion took place d) how the discussion started?

 The answer would be D how the discussion started

Explanation: It says then the girls had a discussion about safety rules. so when it says then it means that they were talking about something that was leading up to the discussion about safety rules. what were they talking about before they started the conversation about safety rules?

c -invasion by the moroccans.

type of error:

the error in the sentence is a "dangling modifier". a dangling modifier is a phrase, word or clause that "dangles" because there is not target to modify. in this case, "after mopping the floor" is the dangling modifier since it has no word to modify. the noun "house" cannot mop the floor; therefore there is a mistake in the writing of the sentence.