Which product of photosynthesis is mainly considered to be waste for plants, although some is used during respiration? A. oxygen
B. carbon dioxide
C. glucose
D. energy

A. Oxygen

Explanation:

A is the only one that makes sense because plants take in carbon dioxide, use glucose for food, and use energy to photosynthesize, and the only answer they don't use is A (oxygen) because they only produce it but not use it

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.