Concept:A question tag is a short question added at the end of a statement. After "Let's" (let us), which makes a suggestion that includes the speaker, the tag is always "shall we?"
Solution:"Let's go out and play" is a suggestion: the speaker invites others to join.
"Let's" = "let us", so the tag must use "we", the people included in "us".
The fixed tag for "Let's..." is "shall we?"
"Will you", "can you" and "would you" use "you"; they suit commands or requests (e.g. "Open the door, will you?"), not a suggestion with "Let's".
Correct sentence: "Let's go out and play, shall we?"
Answer:Option B (shall we)