Answer:
Question 19: complete sentence
Question 18: run-on sentence
Question 19: sentence fragment
Step-by-step explanation:
Question 18 is supposed to be ; Outdoor concerts are very informal. Many people like buying ticketes for them.
Question 17 is supposed to be something like, Because of that, a telescope is going outside the earth's atmosphere to see more clearly.
And There is noting wrong with question 19