1. (C).

If $a_{n-1}-a_{n}=3 n^{2}-37 n-29>0$, then $n \geqslant\left[\frac{37+\sqrt{37^{2}+4 \times 3 \times 29}}{6}\right]+1=14$, which means the sequence starts to strictly increase from the 14th term.
The sequence $\left\{a_{n}!\right.$ has the general term formula $a_{n}=n^{4}-20 n^{2}-10 n+1(n=1,2, \cdots)$, from which term does the sequence $\left\{a_{n}\right.$ start to be strictly increasing?
(A) The 10th term
(B) The 13th term
(C) The 14th term
(D) The 22nd term