Tides describe the regular rising and falling of ocean water. tides are caused by

Tides are the rise and fall of the oceans. They are caused by the gravity, or pull, of the Moon and Sun. The Moon's gravity is the main force in causing tides. It makes the oceans bulge out toward it. Another bulge occurs on the opposite side, because Earth is being pulled toward the Moon and away from the water. The water on the side farthest away from the Moon is least affected by its gravity.

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.

i believe the answer is a.