Mustard gas removes guanine from DNA. For developing embryos, exposure to mustard gas can cause serious deformities because guanine

Mustard gas, a deadly weapon used in WW-I – Deccan News

a
directly causes mutations in DNA.
b
stores the building blocks of proteins.
c
produces energy for DNA replication.
d
is one of the four nitrogenous bases in DNA.

d

is one of the four nitrogenous bases in DNA.