Choose A, B, C, or D for the correct answer.

The following text is for questions 21 to 23.

Materials:

• shoebox
• paintbrush
• black paint
• newspaper
• scissors
• tape
• tracing paper
• thick aluminum foil
• pin

Directions:

1. Paint the inside of the box black, including the lid.
2. Cut a small square out of either endof the box.
3. Cover one of the holes in the box with aluminum foil. Keep the foil tight, and tape down the edges so that no light can get in.
4. Cover the hole at the other end with tracing paper. Again, keep it taped tightly in place.
5. Put the lid on the box. If the fit is not very tight, tape around the lid to hold it in place. Make sure you cover all the gaps.
6. Carefully prick a hole in the center of the foil with a pin. Make the hole as tiny as possible.
7. You have now made a pinhole camera.
8. Finally, point the foil end of your pinhole camera at a suitable scene. Look at the image that is formed on the paper screen.

Adopted from: Tom Jackson, Science Activities Light and Color, Connecticut, Grolier Educational Sherman Turnpike, 2002.

"Carefully prick a hole in the center of the foil with a pin." (Step 6) The underlined word could be best replaced by ____.