"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)
Answer:
Scientists are creating vaccinations that prevent people from getting the bird flu. If the virus mutates, a new vaccine will need to be made. The vaccine needs to be tested, which can be dangerous. It will also take a long time for scientists to know whether the vaccine works or not.
Explanation:
The flu vaccine is injected under skin in a inactive form and the immune system responds with antibodies to the food protecting you from the future exposure to the flu. That's why sometimes you get the flu even though you got a shot because there's different forms of the flu.
Answer: It is number 2 In a population-based sample of 5-to 17-year-olds, 70 percent of obese youth had at least one risk factor for cardiovascular disease
Explanation: I know
