Two Gametes,each Carrying a Mutant Recessive Allele for a Different

Two gametes,each carrying a mutant recessive allele for a different gene/enzyme in the adenine biosynthetic pathway,come together to form a diploid embryo.The individual derived from this embryo will display a:

A) lethal phenotype in media lacking adenine supplementation.
B) wild-type phenotype,capable of synthesizing adenine.
C) a weak adenine requirement for survival (intermediate phenotype) .
D) a profound defect in adenine synthesis as two enzymes are missing.
E) embryonic lethality.