Which is the main reason toads must lay eggs in water?
a. the eggs do not have a shell to prevent water loss.
b. the eggs need to absorb nutrients from water.
c. the eggs are not laid in nests.
d. the eggs need protection from predators.

The answer is A. The eggs do not have a shell to prevent water loss.

Toad's eggs do not have a shell, like reptile eggs or bird eggs. Shell is important because it protects eggs from drying out if they are laid in the land. Toads lay eggs in a jelly-like glycoprotein. Thanks to glycoprotein around toad's eggs, contact with water is maintained all the time so that eggs don't die. 

Carbon-14 has a half-life of 5,730 years and most igneous rock is older than that.