The statement “if a, then b” can best describe as

cause and effect

Step-by-step explanation:

If [an event happens], then [it will trigger another event].

For example:

If [the Great Wall of America is built] then [American taxpayers would have to pay the costs].

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the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents