In this task, find the most appropriate number to replace the blank (indicated with _ ) and express it in words.

[EX Q]: Children are almost _ times as likely to smoke if their parents do.
[EX A]: three

[EX Q]: Diatoms look like _ shells that fit together.
[EX A]: two

[EX Q]: Metals often crystallize in a _ dimensional version of the hexagonal closest packed structure.
[EX A]:
three