1. Several people participated in a test, required to answer five questions, and it was stipulated that those who answered 3 or more questions correctly would be qualified. The test results are: the number of people who answered the first to fifth questions correctly are $81, 91, 85, 79, 74$, respectively, and 70 of these test takers are qualified. Then the number of people who participated in the test is at least ( ) people.
(A) 98
(B) 99
(C) 100
(D) 110
- 1.C.

Let the number of people participating in the test be $n$.
Among these $n$ people, the total number of questions answered incorrectly is:
$$
\begin{array}{l}
5 n-(81+91+85+79+74) \\
=5 n-410 \text{ (questions). }
\end{array}
$$

Since those who answer 3 or more questions incorrectly are considered不合格 (unqualified), the maximum number of unqualified people is $\frac{5 n-410}{3}$, which means the minimum number of qualified people is $\left[n-\frac{1}{3}(5 n-410)\right]$. Therefore,
$$
n-\frac{1}{3}(5 n-410) \leqslant 70 \text{. }
$$

Solving for $n$, we get $n \geqslant 100$.
Thus, the minimum value of $n$ is 100.
Note: 30 people being unqualified is achievable. For example: 15 people answered the first, fourth, and fifth questions incorrectly, 4 people answered the first, third, and fourth questions incorrectly, 9 people answered the second, third, and fifth questions incorrectly, and 2 people answered the third, fourth, and fifth questions incorrectly.