Cactus are adapted to live in deserts and other very dry Places
a) The leaves of the cactus plant are reduced to spines. How does this help it to survive?
b)The stem is large with a space in the centre. How does this help the cactus to survive?

for a

Explanation:

if a cactus has leaves, it will need more water to survive and also there will be a higher rate of transpiration. i don't know about number 2. Try googling it.

the correct answer is b. possesses the characteristic of compartmentalization of organelles, wherein the organelles are bound by membranes.

explanation:

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.