The human ____ is the basic unit of life and performs various functions.

• theory

• produces

• attach

• cell

The virus tries to _____ itself to the host cell to multiply.

• attach

• cell

• contains

• research

The factory _____thousands of products every day.

• common

• attach

• produces

• theory

The immune system ______ to infections by producing antibodies.

• cell

• responds

• attach

• common

The body ______ itself against diseases through the immune response.

• research

• cell

• defends

• theory

Photosynthesis _____ in the chloroplasts of plant cells.

• cell

• theory

• research

• occurs

The book ______ valuable information about space exploration.

• cell

• contains

• attach

• theory

It is ______to catch a cold during winter.

• produces

• attach

• cell

• common

Scientists conduct _____ to find cures for diseases.

• research

• attach

• cell

• contains

The _____ of evolution explains how species change over time.

• attach

• produces

• theory

• cell