Terrell and Astrid Are Working Together Building a Sandcastle at the Beach

Terrell and Astrid are working together building a sandcastle at the beach. They take turns carrying the empty pail to gather sand and collect water and discuss how best to build their sandcastle. Later, Terrell shares his cookies with Astrid, and she gives him have half her sandwich. These children are engaging in

A) solitary play.
B) prosocial behaviors.
C) parallel play.
D) competitive play.
E) reciprocity norms.