The guy above me has it right!
Answer:
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Step-by-step explanation:
Hope this helps:)
They could have assembled total 336 different possible crews.
<em><u>Explanation</u></em>
Total number of trained pilots is 9 and geologists is 4.
The crew should be consisted of 2 pilots and 1 geologist. That means, <u>2 pilots are chosen from total 9 and 1 geologist is chosen from total 4</u>.
Number of ways for choosing 2 pilots from 9
and
Number of ways for choosing 1 geologist from 4 
So, the total possible number of different crews they could have assembled 
Answer:
This is cluster sampling.
Step-by-step explanation:
American Airlines randomly selects 110 flights during a certain week and surveys all passengers on the flights.
This is a type of cluster sampling.
This type of sampling is done by dividing the population into different groups and a simple random sample of clusters is selected from the population.
25% chance of guessing each question correctly
50% chance to guess one correctly