Arteries take blood from the heart. the walls of an artery are made up of thick walls and elastic fibres. veins carry blood the heart and also have valves. the link arteries and veins, and have a one cell thick wall. blood is made up of four main things the liquid part of the blood; red blood cells to carry ; white blood cells to protect the body from disease and to blood clot.

Arteries take blood away from the heart. The walls of an artery are made up of thick muscular walls and elastic fibres. Veins carry blood to the heart and have valves. The capillaries link arteries and veins. Blood is made up of 4 things: plasma red blood cells to carry oxygen, and platelets to help blood clot.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."