Nothing could happen.
1	Nothing	nothing	PRON	NEG-SG	Number=Sing	3	nsubj	_	_
2	could	could	AUX	PAST-AUX	VerbForm=Fin	3	aux	_	_
3	happen	happen	VERB	INF	VerbForm=Inf	0	root	_	SpaceAfter=No
4	.	.	PUNCT	Period	_	3	punct	_	_
