How did mason bees get their name?

A They have a secret handshake
B They use mud to construct their nests
C They only live in fraternal societies

Mason bees build hives in existing spaces like woodpecker holes or hollow trees. They use mud to separate each egg from the next. Each egg cell has its own food provision mass that is consumed before the bees emerge one by one. Thanks for packing a meal, mom!

The correct answer is They use mud to construct their nests.