In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

A person trowels wet concrete on the ground. another person <sep> (A) stands beside him. (B) uses a piece of wood to level the concrete. (C) is choosing the material to put on the walkway. (D) sets a timer on their hand and starts painting a wall.
B