HE HAS WORKED SO HARD RECENTLY; __________ HE IS IN BAD HEALTH. A....

20. He has worked so hard recently; __________ he is in bad health. A. however B. and C. but D. therefore 20. ....

C/ READING.

The excitement of snorkelling in a clear tropical sea is hard to explain to someone who hasn't done it. If you expect to have the opportunity of trying it when on holiday, it is well worth bringing a snorkel if you can get hold of one. Experts now recommend a separate breathing tub.Many swimmers take a deep breath before diving with a snorkel. This is a mistake, because it makes the body so light that you dive with difficulty. It is best to take a couple of deep breaths and then a normal relaxed breath in order to breathe in enough for the dive. Don't take repeated deep breaths before diving because this can lead to a shortage of oxygen, which causes unconsciousness without warning.The back of many snorkellers gets badly burnt, for the snorkellers are so involved in the world below they forget about the danger of sunburn. The sea does not protect your back from the rays of the sun and it is best to wear a T-shirt. Snorkellers should also consider wearing shoes (or flippers), which may protect their feet from sharp rocks