A、Heat it. B、Add oil to it. C、Shake it gently. D、Mix it with water. D短文提到在喝那些糖浆之前要将它与水调配，故选D。

How many of you drink cola? Nearly everyone. Did you know that cola started out not as a soft drink but as a cure for headaches back in the late 1800s? John S. Pemberton, a druggist from Atlanta, had experimented for many months trying to find a cure for the common headache. He worked in his backyard, mixing and heating different combinations of oils and flavors until he found one that seemed promising. Pemberton bottled the mixture and began selling it in drugstores as concentrated sugar liquid that the customer had to mix with water before drinking. Cola’s transformation from sweet medicinal liquid to a carbonated soft drink came about quite by accident. One day, a customer came into a drugstore complaining of a headache and asked for a bottle of cola. He wanted to take it right away. So he asked the clerk to mix the medicine while he waited. The clerk, instead of walking to the other end of the counter to get plain water, suggested mixing it with soda water. The customer agreed, and after drinking it, remarked how good it tasted. The clerk continued offering the mix and carbonated cola grew in popularity. Today carbonated cola is sold in most countries around the world. And although they no longer contain the ingredients used to cure headaches, they are still very refreshing.
16. What does the speaker say about cola in the past?
17. What should customers do before drinking the sugar liquid?
18. How did the customer feel after he drunk the mix?
19. What do we learn about today’s cola?