Can blood go backwards from the right ventricle to the right atrium?

yes

Explanation:

as the atrium contracts , blood flows from your right atrium into your right ventricle through the open tricuspid valve. when the ventricle is full, the tricuspid valve shust . this prevents blood from flowing backward into the right atrium while the ventricle contracts

as the atrium contracts, blood flows from right atrium I to your right ventricle through the open tricuspid valve. when the ventricle is full , the tricuspid valve shuts. this prevent the blood from flowing backward into the right atrium while the ventricle contracts. so the answer is no

1. (1.2kw)x(15/60hours) = .3kwh --> a

2. (5kw)x(90/60hours)x(8cents/kwh) = $0.60 --> d

3. microwave --> 1200 watts = (1.2kw)x(6/60hours) = .12kwh

coffee-maker --> 900 watts = (.9kw)x(10/60hours) = .15kwh

therefore, it requires more energy for the coffee-maker to do the same amount of work.

so the answer is a.

the answer to your question is b