1. Choose the correct answer (7 points per question, total 42 points)
1. The sum of 99 consecutive natural numbers equals $a b c d$. If $a, b, c, d$ are all prime, then the minimum value of $a+b+c+d$ is ( ).
(A) 63
(B) 70
(C) 86
(D) 97
-1 (B).
$$
\begin{array}{l}
\begin{aligned}
a b c d & =x+(x+1)+(x+2)+\cdots+(x+98) \\
& =99 x+(1+2+\cdots+98)=99 x+99 \times 49 \\
& =99 \times(x+49)=3 \times 3 \times 11 \times(x+49)
\end{aligned} \\
\begin{aligned}
\therefore x & =4,
\end{aligned} \\
\text { At this point } a+b+c+d=3+3+11+53=70 .
\end{array}
$$