Which of the following statements is true?

a. we need vitamin d from the sun so there is no unsafe exposure level.

b. from 10am to 4pm are the most dangerous hours for exposure to the sun.

c. there is only one kind of harmful uv ray from the sun.

d. spf 10 is the minimum for safe protection

B. From 10AM to 4PM are the most dangerous hours for exposure to the sun.

Option (B)

Explanation:

The sun releases ultraviolet radiations (UV radiations) which are harmful to the lives on earth and these radiations are constantly controlled by the atmosphere of the earth.

There are 3 different types of UV radiation. They are namely-

Ultraviolet radiation-A -> This radiation is responsible for causing wrinkles, premature aging and also causes skin diseases. This radiation can penetrate the earth's atmosphere and reaches the surface. Ultraviolet radiation-B -> This radiation is highly dangerous as it has the ability to cause skin cancer, but they enter the earth's atmosphere at a relatively very low amount. Ultraviolet radiation-C -> These are harmful radiations but do not reaches the earth's surface as the atmosphere of the earth does not allow to pass through it.

These UV radiations are released significantly between the time of 10 AM to 4 PM. So, exposure to these radiations is harmful.

Thus, the correct answer is option (B).