"To try to write certain sentences is difficult"
The correct statements are 1, 2 and 3.
1) The sentence is correctly written. The pattern "to try to do something" is correct and can be used.
2) The sentence contains more than one infinitive. It contains two infinitive verbs. TO TRY and TO WRITE.
3) One infinitive is inside another infinitive phrase. "To try to write certain sentences" is an infinitive phrase, it functions as a noun because it is the subject of the sentences. So, the second TO INFINITIVE is inside the main infinitive phrase. (That is the reason why number 4 is not correct)
Starr Carter is the sixteen-year-old protagonist of The Hate U Give. The novel is presented in the first person from her point-of-view. Starr lives in the urban neighborhood of Garden Heights, but attends private school in a nearby affluent neighborhood called Riverton Hills. This results in a split identity for Starr. She monitors her speech and behavior among her white peers, because she is one of the only African American students at the school, and she feels like she must represent her entire race. In other ways, Starr is a typical teenager; she loves basketball and the Fresh Prince of Bel-Air, she is fashion conscious, and she has a Tumblr blog. She thinks her parents are corny, but secretly admires them.
Source: http://www.bookrags.com/studyguide-the-hate-u-give/characters.html#gsc.tab=0
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