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Which gas is transported by the circulatory system in humans and is used by cells during respiration to release energy stored in food?

• carbon dioxide

• nitrogen

• hydrogen

• oxygen

What is the main organ of the circulatory system?

• small intestine

• bone

• lungs

• heart

What is the main organ of the circulatory system?

• small intestine

• bone

• lungs

• heart

Arteries carry oxygen rich blood away from the heart.

• True

• False

Veins carry oxygen poor blood back to the heart.

• False

• True

The job of the heart is to . . .

• pump blood around the body.

• send food to the small intestines.

• break down food.

• give energy to the body.

______________ are the smallest blood vessels.

• Arteries
• Veins
• Capillaries

______________ are the second largest blood vessel. 

• Arteries
• Veins
• Capillaries

The circulatory system works with the __________ system to obtain energy from nutrients that we eat. 

• respiratory 
• digestive
• skeletal
• nervous

Which system permits blood to circulate and transports nutrients around the body?

• Nervous
• Respiratory
• Circulatory
• Digestive