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2

First of all, look at how many possibilities a student can subscribe to a magazine: that is, the arrangement and combination of A, B and C, and the total * * * is 3+3+ 1=7 possibilities.

This topic is equivalent to putting 100 people into seven boxes, and at least how many people are in the same box.

Then it is 100/7= 14+2.

In order to minimize the number of people in the box, the last two people should be scattered in seven boxes.

The same number of people is at least 14+ 1= 15.

In other words, at least 15 students subscribe to the same magazine category.

three

Solution: First of all, analyze how many kinds of combinations children can take with two kinds of fruits at will. There are four kinds of two fruits (two apples, two pears, two peaches and two oranges) and six kinds of two fruits (apple and pear, apple and peach, apple and orange, pear and peach, peach and orange). So fruit * * * has 4+6= 10 different combinations. Look at the 10 drawers. These drawers have different combinations of 10.

81÷10 = 8 ...1(pieces).

According to the pigeon hole principle, it is not easy for at least 8+ 1=9 children to answer the same question with fruit.