Is asexual reproduction when the offspring is identical to one parent, an offspring that looks like a combination of both parents, or an offspring that looks like half of each parent?

it's when the offspring is identical to one parent

Explanation:

asexual reproduction only requires one parent, therefore being identical to it.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

b is the correct answer