| Most growing plants contain much more
water than all other materials combined. C. R. Barnes has suggested that it is
as proper to term the plant a water structure as to call a house composed mainly
of brick a brick building. Certain it is that all essential processes of plant
growth and development occur in water. The mineral elements from the soil that
are usable by the plant must be dissolved in the soil solution before they can
be taken into the root. They are carried to all parts of the growing plant and
are built into essential plant materials while in a dissolved state. The carbon
dioxide from the air may enter the leaf as a gas but is dissolved in water in
the leaf before it is combined with a part of the water to form simple
sugars—the base material from which the plant body is mainly built. Actively
growing plant parts are generally 75 to 90 perce A. (A) forming sugars B. (B) sustaining woody stems C. (C) keeping green D. (D) producing carbon dioxide [单项选择]People are living much longer lives than ever before but not all enjoy their golden years. Forgetfulness or dementia, long accepted as a part of growing older, is actually not a natural consequence of old age. Some people actually stay as sharp mentally as they ever were but it doesn’t come by accident. Mental acuity can be safeguarded throughout our lives in many ways.
Get physical. Maintaining a reasonable level of physical activity does more than keeping our bodies in shape. Activity helps us to release endorphins (the feel good hormones) which make people of all ages function more efficiently. Recent studies have found that exercise also keeps our mental functioning in shape. Read. People who enjoy reading are using their minds and their imaginations. They are learning with each page they turn. Talking books are available if you can’t see as well as you used to. The benefits will be the same. Watch TV to stay sharp rather than zone out. Playing along with trivia game show A. walking out of the room B. pace up and down some place C. tend to fidget D. be absent-minded 我来回答: 提交
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