Blowing bubbles(泡泡) is fun！The best thing about bubbles is that it’s easy to make your own bubble solution(溶液)．You can make as much as you want and blow as many bubbles as you’d like.If you add a “secret” ingredient(配料)，you’ll get bigger and stronger bubbles! Do just as follows：
Measure 6 cups of water into one container，then pour 1 cup of dish soap into the water and slowly stir it until the soap is mixed in.Try not to let bubbles form while you stir.
Measure 1 tablespoon of glycerin(甘油) or 1/4 cup of corn syrup(玉米糖浆) and add it to the container.Stir the solution until it is mixed together.
You can use the solution right away，but to make even better bubbles，put the lid on the container and let your super bubble solution sit overnight.The soap mixture on the outside of a bubble is actually made of three very thin layers：soap，water，and another layer of soap.A bubble pops when the water that is trapped between the layers of soap evaporates(蒸发)．The glycerin or corn syrup mixes with the soap to make it thicker.The thicker skin of the bubbles keeps the water from evaporating as quickly，so they last longer.It also makes them stronger，so you can blow bigger bubbles.
Dip a bubble wand or straw into the mixture，slowly pull it out，wait a few seconds，and then blow.If you don’t have a ready­made “bubble wand”，you can make your own by cutting off the end of the bulb of a plastic pipet.Dip the cut end in solution and blow through the narrow end.You can also make a loop out of thin wire or pipe cleaner.Just twist a round end on your wire to blow the bubbles through.You can even make it heart­shaped，square or use other shapes if you’re clever enough to bend it well.
28．For what purpose is the text written?
A．To argue.     B．To advertise.   C．To entertain.    D．To instruct.
29．What does the secret in making bigger and stronger bubbles lie in?
A．The soap.              B．The corn syrup.
C．The water.            D．The straw.
30．What can you use a bubble wand to do?
A．Blow bubbles.         B．Mix the solution.
C．Measure soap.         D．Shape wires.
31．What can we infer from Paragraph 4?
A．More soap，more bubbles.
B．Less water，better bubbles.
C．Stronger skin，more bubbles.
D．Thicker layers，bigger bubbles.
28-31DBAD