alleryDuring systole
AThe aorta closes its valves completely shut
BThe heart chambers relax and fill with blood
CThe heart chambers contract and push blood out
DThe vena cava reverses its flow direction
Answer & Solution
Correct answer: C. The heart chambers contract and push blood out
1. The chapter section on heart action defines systole and diastole.
2. Systole is the contraction phase.
3. Ventricular systole pumps blood into arteries.
4. Diastole is the relaxation phase, when chambers refill.
_Source: Selina Concise Biology Class 10, Ch 7 The Circulatory System (Mistral OCR'd PDF), section on systole/diastole_
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