问题
单项选择题
心源性呼吸困难最早出现的是
A．劳力性呼吸困难
B．夜间阵发性呼吸困难
C．端坐呼吸
D．吸气性呼吸困难
E．呼气性呼吸困难
答案
参考答案：A
解析：心源性呼吸困难按严重程度，分为：劳力性呼吸困难、阵发性夜间呼吸困难、端坐呼吸、心源性哮喘、急性肺水肿。劳力性呼吸困难最早出现。
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心源性呼吸困难最早出现的是
A．劳力性呼吸困难
B．夜间阵发性呼吸困难
C．端坐呼吸
D．吸气性呼吸困难
E．呼气性呼吸困难
参考答案：A
解析：心源性呼吸困难按严重程度，分为：劳力性呼吸困难、阵发性夜间呼吸困难、端坐呼吸、心源性哮喘、急性肺水肿。劳力性呼吸困难最早出现。
| The most popular organic gem is the pearl. A pearl is the response of a marine mollusk to the presence of an irritating impurity accidentally introduced into its body; a cultured pearl is the result of the intentional insertion of a mother-of-pearl bead into a live mollusk. Whether introduced accidentally or intentionally, the pearl-making process is the same: the mollusk coats the irritant with a substance called nacre. Nacre is composed chiefly of calcium carbonate. Because very few natural pearls are now on the market, most pearls used in free jewelry are cultured. These include "Biwa" pearls and most other freshwater pearls. Cultured pearls are not easily distinguished from natural pearls except by an expert. |
Nacre is a substance that is ______.
A．mechanically manufactured
B．the result of laboratory testing
C．organically secreted by the mollusk
D．present in the chemical composition of freshwater pounds