35-23 Cut a piece of paper into 5 pieces, from the resulting pieces take several pieces, each cut into 5 pieces; then from all the pieces take several pieces, each cut into 5 pieces; continue this process until after a certain cut you stop. The total number of paper pieces could be
(A) 1990.
(B) 1991.
(C) 1992.
(D) 1993.
(9th "Jinyun Cup" Junior High School Mathematics Invitational Competition, 1992)
［Solution］Since each piece of paper is always divided into five after being taken out, i.e., it increases by 4 pieces, the total number of paper pieces increases by $4 k$ after taking out $k$ pieces of paper. Initially, the number of paper pieces is $1+4$, so the total number of paper pieces at this time is
$$
1+4+4 k=1+4(k+1),
$$

which means the total number of paper pieces after cutting always remains in the form of $4 n+1$.
$$
\because 1993 \div 4=498 \cdots \cdots 1 \text { or } 1993=4 \cdot 498+1 \text {. }
$$

Therefore, the correct choice is $(D)$.