15. positive a.

(1) 肯定的；确切的
He gave me a positive answer as to whether he would come.
I would like to give you a positive instruction.

(2) 有把握；肯定（作表语）
The boy was very positive about what he said.
I am positive that one day people's attitude towards daydream will be changed.
Are you positive of it ?

(3) 积极的；建设性的
What we need is a positive idea.
Positive suggestions are welcomed anytime.

(4) 正的；阳性的
The positive sign is "+".
Light is positive, darkness is negative.
光是阳性的，黑暗是阴性的。

16. due to

(1) 应给予；属于
A great deal of money is due to you.
Our grateful thanks are due to you.

(2) 由于；因造成（作表语）
The difficulty facing us is due to our ignorance.
The accident is due to his carelessness.

(3) 由于（作状语）
He failed due to carelessness.
Due to the change, a scheduled visit to the factory has to be cancelled.

(4) 用于in due course (time) 结构：在适当的时候
You will realize all this in due time.
Spring arrives in due course.