The answers are:
A. DNA replication in the nucleus of a cell
B. From one helix of DNA in a replication process, we get two: The DNA is a double helix and it consists of two strands of specifically connected amino-acids. When the time for replication comes, a set of enzymes unwind the two strands and leave them as a base for additional two strands attaching to them - the green line is an example of that. The free nucleotides - adenine, guanine, thymine and cytosine are left open and the enzyme called DNA-polymerase helps to produce a new strand on the template of the old parental one (one of the blue ones in the picture)
C. By the location on the smaller picture - replication takes place in the nucleus. And the most important hint are the letters A - adenine, G - guanine, T- thymine, and C-cytosine. A connects with T, and G connects with C.
Answer:
water-vascular system
Explanation:
Echinoderms exhibit several unique features and the presence of a water vascular system is one of them. The water vascular system of these organisms consists of a network of fluid-filled canals and chambers. The marine water enters and exits the system through an opening. This system functions as a hydrostatic skeleton during locomotion.
Tube feet of these organisms are filled with fluid as water enters into them via the canals of the water vascular system lead to them. This inflates the tube feet and serve in locomotion. The water entering through the water vascular system also brings in dissolved oxygen and food particles into the body.
The body's most important nonspecific defense against pathogens is the skin. The nonspecific defense system in the body guards against keeping infections from the body. Some of the nonspecific defenses are tears, mucus, and sweat among others. The correct answer will be D.