Nitrogen in the atmosphere must be "fixed before it can be used by plants. Atmospheric nitrogen is "fixed by
plants.
bacteria
bacteria and insects.
D)
bacteria and lightning

answer by yourhope:

hi! : )

in which structure in the nucleus are ribosomes made?

b) nucleolus!

: )

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.