What is Escerichia Coli's effect on humans? a. Usually harmless
b. Sometimes pathogenic
c. Always dangerous
d. Rarely helpful

I think it is C.

Explanation:

coli that make the toxin are sometimes called STEC, which is short for “Shiga toxin-producing E. coli.” One especially bad strain, O157:H7, can make you very sick. It causes abdominal cramps,vomiting, and ect

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.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".