I literally don’t understand this help me

For a school newspaper article, cienna conducted a survey to find out students’ favorite subjects. she polled all the students in mrs. lopez’s advanced dance class. why is her data likely to be skewed? honors dance students are more likely to enjoy dance than students in the general population, so dance may be overrepresented. cienna should have interviewed all the students in the school to get more accurate data. honors dance students are more likely to enjoy dance than students in the general population, so dance will be underrepresented. cienna should have interviewed only every other student in the class to avoid having too many people.

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years