Fact 1: An egg requires warmth to survive.

Fact 2: First the frog lays the eggs, then the warmth from the sun makes the eggs hatch into baby tadpoles.

Given the two facts above, answer the question "What heats frog eggs so that they may hatch into tadpoles?" with the following options: 
- sun's heat
 - heat
 - the sun
 - geothermal vents
 - Cooking
 - the mother frog
 - the father frog
 - sunlight


 

   the sun      