A recessive trait is defined as A. one that is expressed when the dominant allele is not present.

B. one that is never expressed.

C. one that is always expressed.

D. one that is expressed whenever it is present.

Recessive traits are traits carried in a persons genes without being expressed because they are masked by the dominant trait. Therefore the answer is A.

Explanation:

Recessive traits can be expressed so B is incorrect. It is not always expressed so C is incorrect. Just because a recessive trait is present does not mean it will be expressed, and if that were true it would always be expressed, so D is incorrect as well.

"do a testcross with a homozygous recessive plant."

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.