Correct the given sentence gramatically.

Shreya, who she is my best friend, is a singer.

In the following question, out of the four alternatives, select the alternative which will improve the bracketed part of the sentence. In case no improvement is needed, select "no improvement".
I gave up (drinks) many years ago.

In the following question, out of the four alternatives, select the alternative which best expresses the meaning of the idiom/phrase.
Beat a dead horse

In the following question, out of the four alternatives, select the alternative which best expresses the meaning of the idiom/phrase.
At the drop of a hat

In the following question, out of the four alternatives, select the word opposite in meaning to the word given.
Summon

In the following question, out of the four alternatives, select the word opposite in meaning to the word given.
Sullen

In the following question, out of the four alternatives, select the word similar in meaning to the word given.
Subtle

In the following question, out of the four alternatives, select the word similar in meaning to the word given.
Stupor

In the following question, the sentence given with blank to be filled in with an appropriate word. Select the correct alternative out of the four and indicate it by selecting the appropriate option.
At night, the winding roads can make driving up the mountain a ______________ journey.