Answer:
A sentence fragment.
Step-by-step explanation:
All sentences must have a subject, a verb, and an object.
He (Subject)
Giggled (Verb)
Missing: Object (Why did he giggle?
(He) (giggled) ( because he thought it was funny.) (Sentence)
(He) - Subject
(giggled) - Verb
( because he thought it was funny.) - Object , it told me why he giggled.