Which job do white blood cells do inside your body?

• They store harmful germs for the body to use.
• They help find and fight harmful germs.
• They carry oxygen instead of fighting germs.

Which outer layer of your body forms a barrier against many germs?

• Your skin
• The blood
• The bones

Some vaccines use weakened or inactive germs to train an immune response.

A person's white blood cells are fighting germs, but the person still becomes ill. Which explanation fits the lesson?

• The defences do not stop every infection.
• White blood cells defend only the outer skin surface.
• Becoming ill means no white blood cells are responding.

Tom cuts his knee while playing. Why can germs enter more easily through the cut?

• The cut trains cells to recognise germs.
• The cut removes every immune defence from his body.
• The cut leaves a gap in the skin barrier.

Why can a vaccine help protect you from a disease you have never had?

• It makes skin thicker to block germs.
• It helps the body remember a specific germ.
• It removes all germs forever so immune cells are no longer needed.

Without a vaccine against a disease, white blood cells cannot fight the germ that causes it at all.

Priya says, 'Bacteria and viruses can cause illness, so both must be living cells.' Which statement corrects her idea?

• Both are living cells that can cause illness.
• Viruses are living cells; bacteria need living cells to multiply.
• Bacteria are cells; viruses need living cells to multiply.