<span>I think the answer is A test cross can be used to: study how traits are inherited. </span>
The correct answer for the question is B. Fossil.
Fossils are remnants, traces of animals or plants, from the past ages that have been preserved. Fossils may be classified as cast and mold fossil, insect preserved in amber, petrified wood, compression fossil of a fern and pyritized ammonite.
Answer:
Active uptake (which I think you mean active transport) is important when the concentration gradient is against that of a certain substance, so it doesn't cross the membrane through diffusion or passive transport. It is sometimes necessary if a substance needs to move across a membrane but can't do so due to electrical charge or that there is a substance on the other side of the membrane preventing diffusion.
Explanation:
