The correct answer is A.
Gravitational force will attract any object with mass. It's why you're not floating in the air right now, but rather making contact with the ground. At the same time, since you have mass, you're also attracting other objects right now with gravitational force.
<span>This change is called BOILING.</span>
The activation energy is the minimum required energy in order to start a reaction. It is the barrier to break to enable reactants to form products. It is not important only for some reactions but to all reactions. This energy should be supplied or reached first before we observe a reaction to happen.
