In the trp operon, tryptophan serves as a(n) , binding to the repressor and causing it to block to attachment of RNA polymerase. a. operator
b. inducer
c. repressor
d. corepressor
e. gene

The answer is A

High tryptophan: The tryptophan binds to the trp repressor and causes it to change shape, converting into its active (DNA-binding) form. The trp repressor with the bound tryptophan attaches to the operator, blocking RNA polymerase from binding to the promoter and preventing transcription of the operon.

because the light is a great source of energy for the plants to survive. (i hope this )