What is the Causative Agent in the Formation of a Cyclobutane

Question

What is the causative agent in the formation of a cyclobutane thymine dimer?
A)benzo[a]pyrene
B)N-methyl-N'nitro-N-nitrosoguanidine
C)methylnitrosourea
D)ethylmethanesulfonate
E)ultraviolet radiation

Accepted Answer

A cyclobutane thymine dimer is formed by the covalent linkage of two adjacent thymine bases in DNA caused by exposure to ultraviolet (UV) radiation. UV radiation causes the thymine bases to form a dimer through the formation of a cyclobutane ring between the two adjacent thymine bases.