Amoebas can change their shape. Amoebas need humans to survive. Amoebas look just like human cells. Amoebas are made of only one cell.
I gave my students this multiple choice question: People without safe drinking water may get an illness called dysentery. Dysentery is caused by a type of amoeba that lives inside the body. Doctors can find these amoebas by looking at body samples under a microscope. Which characteristic of amoebas best explains why doctors use microscopes to find dysentery amoebas?

Only one answer is correct among these 4 choices:
- Amoebas can change their shape.
- Amoebas need humans to survive.
- Amoebas look just like human cells.
- Amoebas are made of only one cell.

Could you tell me which one is correct?

Amoebas are made of only one cell.