Answer:
C.  Marriage was the only means for women to gain social mobility.
Explanation:
Jane Austen's time is the 1600s where women had very limited professional development. In such a very patriarchal society, women were inferior and their only chance at improving their status in life was marrying a man of certain stature; although marriages were still arranged then. They had no voice of their own and they were not even allowed to vote.
 
        
             
        
        
        
Answer:
D. Governments must join people in fighting for a sustainable climate.
Explanation:
In his Nobel Prize Speech, Gore compares the inaction displayed by world leaders against Hitler, to the inaction displayed by world leaders against climate change. Also I took the test. Have a nice day :)
 
        
             
        
        
        
The only preposition in the options available to you is of, so the correct answer is C.
A) and B) are conjunctions.
D) is an adverb. 
        
             
        
        
        
The essential appositive in the sentence "astronomer maia mitchell discovered a comet in 1847 and went on to become the first professional female astronomer in the united states," is Maia Mitchel. The last option is correct. 
An appositive consists on a noun or noun phrase that renames another noun right beside it. The appositive can be a short or long combination of words.
In this particular case, the words Maia Mitchell which is a proper noun is renaming the noun astronomer, which is right before it and constitutes the subject of the sentence.