Why is the expression past history incorrect

What is the best meaning for obscure in this line from the passage? a) ancient b) dark c) royal d) unknown

Question 3 of 10 points which sentence is an example of chronological structure in "the city without o a. without daily pumping, manhattan's subway tunnels would be flooded o b. some time in the next 100,000 years, glaciers will cover all of manhattan o c. central park has a garden that houses plants mentioned in shakespeare's plays. o d. if flooding were to go unchecked, steel support beams in buildings would rust

Which word in the sentence is the object of the preposition ? scrape the dishes and put them in the sink 1)in 2)them 3)dishes 4)sink