A botanist selects n^2 trees on an island and studies (2n + 1) trees everyday where n is an even integer. He does not

[BTGmoderatorDC]

A botanist selects n^2 trees on an island and studies (2n + 1) trees everyday where n is an even integer. He does not study the same tree twice. Which of the following cannot be the number of trees that he studies on the last day of his exercise?

A. 13
B. 28
C. 17
D. 31
E. 79



OA C

Source: Princeton Review

[regor60]

Poorly worded question.

As worded, it states that 2K+1 trees are studied every day.

Every day includes the last day, by definition, lol.

This could lead to the natural short cut solution that since 2k+1 is always odd, 28, answer B cannot be the last day.

The question leaves unsaid that the last day can be a remainder, less than 2k+1.