Answer:
its because of gravity of earth.
number 4 can be easily related to current event as the BLM movement is trying to destroy monuments and remove the history of slavery from our school textbooks, if there's no history to learn from, we will not learn from our mistakes and we will make them again
D. We collected shells because we wanted to use them to make a necklace.
The crowd, because it identifies a group of people and still sounds like a singular noun.