$\"\"$

The series $\"\"$

Find the first differences of consecutive terms.

$\"\"$

The common difference is not constant.

Find the second differences of consecutive terms.

$\"\"$

The common difference is constant.

Hence the sequence is geometric sequence.

$\"\"$

$\"\"$ term of a geometric sequence: $\"\"$ .

Find the $\"\"$ term of this sequence.

$\"\"$ (Substitute $\"\"$ and $\"\"$ )

Find the $\"\"$ term of the sequence.

$\"\"$ (Multiply: $\"\"$ )

$\"\"$

Option C is right choice.