18. induced pluripotent stem cells are cells from adults that have been reprogrammed to imitate embryonic stem cells. why might induced pluripotent stem cells be a valuaale tool in science and medicine? o a. induced pluripotent stem cells can become any cell type in the body, but are from adults, avoiding the controversies associated with embryonic stem cells o b. induced pluripotent stem cells are the only type of stem cell that's truly pluripotent. o c. induced pluripotent stem cells may become any cell type in the body, but are fraught with ethical questions over their use. o d. induced pluripotent stem cells are derived from adult cells and therefore may have dna abnormalities, allowing scientists to understand the effects of sun exposure or toxins on dna

A

Explanation:

Due to ethical problems in using embryonic stem cells of killing a life, ipsc are used by reporgramming a adult stem cell by using appropriate molecular signals to 'reverse the silenced genes', reverting the adult stem cell back to being a multipotent or pluripotent stem cells.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

the answer is:

carbon dioxide