Which of the following is a way to conserve water ?
a . taking longer showers
b . reusing water in a factory to cool hot machinery
c . letting the water run while you brush your teeth
d . using open ditches to carry water for irrigation

Option (B) is the correct answer.

Explanation:

Conservation of water means to avoid wastage or unnecessary use of water.

For example, taking longer showers is actually unnecessary use of water.

Whereas when reusing water in a factory to cool hot machinery then it means we are utilizing waste water to carryout a certain task.

Hence, it means we are conserving water.

Thus, we can conclude that reusing water in a factory to cool hot machinery is a way to conserve water.

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.