If it is "the possibility of black holes", then the answer is "direct object". "Many scientists" is the subject, there is no "predicate noun" because there is no linking verb here, there are no adverbs in this sentence, nor adjectives, and the object of a preposition would be "black holes", because it follows a preposition OF.
Spinning wheel, of course! That was invented long before the 1900's!
Hope that I could help
Answer:Following the failure of a French construction team in the 1880s, the United States ... The project was helped by the elimination of disease-carrying mosquitoes, while chief engineer John ...
Explanation:Following the failure of a French construction team in the 1880s, the United States ... The project was helped by the elimination of disease-carrying mosquitoes, while chief engineer John ...
C- California became a state in 1850 after meeting the required population to apply for state status