Which force is sometimes attractive and has an infinite range?
a) strong nuclear
b) weak nuclear
c) gravitational
d) electromagnetic

D) electromagnetic

Explanation:

First of all, we can exclude the following two options:

A) strong nuclear

B) weak nuclear

In fact, these two forces do not have an infinite range, so they cannot be the right option.

We have now two options: gravitational force and electromagnetic force. However, we notice that:

- Gravitational force is always attractive: it acts between every object with mass, and it is always attractive

- Electromagnetic force is sometimes attractive, sometimes repulsive. In particular, it is attractive when we have two charges of opposite sign, and it is repulsive when we have two charges of same sign.

Therefore, since the text of the question says "it is sometimes attractive", the correct option is

D) electromagnetic

less than one you can't create energy