Answer:
C.
Explanation:
Radiation occurs whithout touching. This specific form of radiation is called thermal radiation.
Answer:
A
Explanation:
You must know the basics of Trigonometry to solve this.
First, you must know that

lies in the second quadrant, so sin is negative.
Next, since
pi/4, is the reference angle of 3 pi/4, this means that we can set up a right triangle with pi/4 as an angle, we get


So the answer is A