Pl need choose the best word to complete the sentence. the most striking thing about her , however, was an incessant twitching of the mouth and eyebrows, a form of nervous disorder resulting from isolation and monotony, and from frequent physical suffering. a. scourged b. legacy c. physiognomy d. alight

C. Physiognomy- a person's facial features or expression, especially when regarded as indicative of character or ethnic origin.

C) Physiognomy

You can tackle this question by putting in the answers and seeing if they fit the context of the sentence. The sentence is describing the woman's physical features - her twitching of her mouth and eyebrows. That means were looking for a word that basically means facial features, or something like that. 

If, like me, you weren't sure what some of these words meant, you can start by eliminating options that you know aren't right, or looking at words that could fit. I knew from the "physio" part of the word that it meant something to do with the human body. But say you didn't know that, you could just eliminate the other answers:
A is wrong because scourged is a verb meaning "to cause suffering," and not a noun. B is quite a common word, so you probably know the woman's legacy isn't something on her face that you could see. D, alight, means "to descend from the air," and it's also a verb, and you're looking for a noun.