The part of the human gut that has an acidic content is the?

I. Stomata → Spirogyra II. Alveoli → Earthworm III. Malpighian tubule → Mammal IV. Contractile vacuole → Protozoa.
Which of the above structures is correctly matched with the organisms in which it is found?

A food chain always begins with a?

Mycorrhiza promote plant growth by?

The barrier between maternal and fetal blood is the?