A stands out most to me, CO comes from the air and air is basically oxygen we breath. When we exhale CO comes out (of course). I would say A is correct.
Answer: B. secrete enzymes that kill bacteria
Explanation:
Paneth cells, so-called because they were first described by Dr. Josef Paneth in 1888, are pyramidal cells, with the nucleus in the basal position, and with large granules in the apical position. Its first isolated specific product was the lysozyme, a bactericidal substance, by Alexander Flemming. These cells play an important role in innate immunity in the small intestine, producing a wide diversity of antimicrobial peptides and enzymes such as lysozyme itself, cryptidines, defensins and a lectin with bactericidal properties.
Answer: The below are following hazards of four-legged animals and fish.
Explanation:
The four legged animals like cats, dogs, horse, and others need proper shelter, food, and care to survive.
They need to be taken outdoors for excretion, and walk.
The mating period is not fix and not easily done.
The four like fishes like turtle and squid are difficult to be handled in aquarium.
The four legged fishes do not come in fishing net during aquarium cleaning.
There are chances of being biten by four legged animals and their associated diseases like rabies.
These animals can lick the food we eat and contaminate the food.
The animal feces may produce air pollution.
The animal noise like dog bark can cause noise pollution. Thus can lead to problem of hypertension.
The beginnings of a brain first become apparent around four weeks after conception when the neural plate folds to form the neural tube
I'd say probably Biomass, not 100% sure but it's renewable, but it can create power and heat.