1. Jude, 7, asks: how many spikes are on the biggest cactus in the world?

   1. About 8 million

   2. Just 42

   3. More than 10 million

   4. Many thousands of spikes, depending on how many arms it has and how old it is

2. Oscar, 7, asks: why do people hunt animals for their tusks, like elephants and narwhals?

   1. Tusks taste delicious

   2. Tusks are made of ivory, which is very valuable

   3. They’re a popular alternative to bricks

   4. They’re great toothpicks

3. Tovah, 5, asks: why does people’s hair turn grey when they get older?

   1. Because old people stop colouring in their hair with felt tip pens

   2. They wash their hair too much

   3. It shows that they’re wise

   4. Because the hair stops producing pigment

4. Myla, 12, asks: how do lips get chapped?

   1. Fairies steal lip moisture to polish their wings

   2. From talking too much

   3. Lips don’t have oil glands and dry out easily in cold or dry air, or in the wind

   4. Eating too many bananas dries them out

5. Jack, 11, asks: what is the longest surgery performed on a human?

   1. A two-week operation to replace all someone’s bones

   2. A five-day surgery to hook up extra arms

   3. An eight-day surgery to attach an extra head

   4. A 103-hour surgery to separate conjoined twins

Solutions

1:D - The saguaro cactus, the largest cactus species in the world, can grow to more than 12 metres tall, and may have many thousands of spikes, especially if it has many arms., 2:B - Ivory is a hard, white material from the tusks of animals like elephants and narwhals. People hunt these animals illegally because ivory can be sold for lots of money and used to make jewellery or statues. Sadly, this has made some animals endangered., 3:D - Melanocytes are the cells that produce the pigment responsible for skin and hair colour. As people age, the melanocytes at the base of each hair slow down or stop producing pigment. Without the pigment, hair appears grey, silver or white., 4:C - Unlike the rest of your skin, lips have no oil glands, so lose moisture easily. Cold weather, wind, sun and even licking your lips too much can dry them out. , 5:D - In 2001, a team of doctors in Singapore performed a surgery lasting 103 hours (more than four days) to separate conjoined twins from Nepal. It was extremely complex, requiring careful teamwork.

Scores

1. 5 and above.

2. 4 and above.

3. 3 and above.

4. 2 and above.

5. 0 and above.

6. 1 and above.