I think the best answer is:
<span>A. Tigers from adjoining populations will immigrate into the geographical area of this population.</span>
<span>All mammals have at least one X chromosome. Female mammals have two X chromosomes, so each of her eggs has a single X chromosome. Male mammals have XY chromosomes, meaning they can generate sperm containing the X chromosome, or sperm containing the Y. If the egg receives sperm containing the X chromosome, then the resulting individual forms ovaries, and is female.</span>
Cephalochordates reproduce by releasing their eggs and sperm into the water, where they are fertilized externally. The fertilized eggs develop into free-swimming larvae that drift in the water for up to 200 days, feeding on plankton and other suspended matter, before settling down as adults.
A cell membrane. Cell membranes are phospholipid bilayers (a.k.a 2 layers of phospholipids)
<span>advancing mass of warm air, in particular, the leading edge of the warm sector of a low-pressure system.</span>