Have become is the answer
Ok, so “is” is the linking verb and I’m pretty sure the predicate is... effective? I’m not sure tbh! But I really do think it is that. I’m sorry if it is incorrect. My apologies.
It represents the moral and social decay that results from the uninhibited pursuit of wealth, as the rich indulge themselves with regard for nothing but their own pleasure. The valley of ashes also symbolizes the plight of the poor, like George Wilson, who live among the dirty ashes and lose their vitality as a result.
Answer:
The killer had left a trail of blood on the floor
