7. e and f
9. c.
sorry didn't understand 8
Answer:
The null hypothesis is
.
The alternative hypothesis is 
Step-by-step explanation:
Suppose that a recent article stated that the mean time spent in jail by a first-time convicted burglar is 2.5 years.
At the null hypothesis, we test if the mean is of 2.5 years, that is:

A study was then done to see if the mean time has increased in the new century.
At the alternative hypothesis, we test if the mean has increased, that is, if it is above 2.5 years. So

The answer to your question is 4 minutes
The correct answer is B. So for A, 8m is smaller than 12 m. For B, 20 m is Bigger. For C, Find how many meters is 1 centimeter, the answer is 1 cm : 12m, the meter is not bigger than 12, but the same, so C is wrong. For D, divide both sides by 3 to find 1 CM, the answer is 1 cm : 5 m, it is wrong.