It's False – they lay eggs which they bury in a shallow hole. The temperature at which the eggs then incubate makes a difference to whether the babies become males or females.

It's False – Yours stomach secretes hydrochloric acid to help digest food.

It's False – Salt in the sea comes from minerals washed off the land by rivers over millions of years. But the levels of salt are no longer rising because if the levels climb any higher, chemical reactions kick in which remove salt again and lock it away in new mineral deposits.

It's True – Alexander Fleming extracted penicillin from the penicillium mould after he accidentally discovered that it could kill bacteria.

It's True – a tiny part of the brain acts as a body clock which tells us when to go to bed and when to wake up. It is reset by signals from your eyes but not immediately which is why you feel tired or ‘jet lagged’ when you first go abroad somewhere.