Step 1: Distinguish primary vs secondary.
Primary groups are small, intimate, face-to-face (family, close peers). Secondary groups are larger, formal, goal-oriented (class, club), with impersonal, role-based ties.
Step 2: Apply to “play group.”
A children’s informal peer circle (playmates) functions as a primary group. However, school/creche “{Play-Group}” organised under formal rules, supervision, timetables and goals acquires secondary characteristics.
Step 3: Conclude.
Because the stem does not specify informal vs institutional setting, the safest choice is Both (A) and (B).
\[
\boxed{\text{Option C}}
\]