Question

1. what are machines fueled by?

sun
gasoline only
electricity only
energy

Explanation:

Machines require energy to operate. Energy can come in various forms such as electrical energy (for electric machines), chemical energy (like gasoline for internal - combustion engines), solar energy (for some solar - powered machines), etc. The sun is a source of energy (solar energy), but it's just one type of energy source. Gasoline and electricity are also forms of energy but are not the only ones. So, in a general sense, machines are fueled by energy.

Answer:

Energy