题干

人类生存离不开空气,下列说法正确的是(   )

A:空气中可吸入颗粒物(PM2.5)的多少不影响人体健康

B:空气是由多种物质组成的混合物

C:空气中二氧化碳的体积只占0.03%,因此它的作用很小

D:空气中氮气的质量分数为78%

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答案(点此获取答案解析)

B

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    A cat is recovering in California after surviving a 6,500-mile journey across the Pacific stowed inside a Chinese shipping container without food or water. Staff and volunteers have named it “Ni Hao”, which is Chinese for “hello”.

    It was discovered breathing shallowly after a two-week trip across the Pacific Ocean. The cat was seriously suffering from loss of water and starvation when the container was opened in California last week, but was said to be doing well after being sent to the Carson Animal Care Centre in Los Angeles. At first it was too weak to stand, but finally took its first steps. Then it ate a good meal and slept soundly. The cat woke up on Thursday morning, physically in a better condition than 24 hours ago.

     “Ni Hao greeted the medical team with its first meow this morning and is attempting to stand,” said Marcia Mayeda, head of the Los Angeles Department of Animal Care and Control. Aaron Reyes, director of the Department, added, “We finally got to hear its voice. It sounds like a single-engine plane.”

    Ni Hao is expected to be observed for 60 days but afterwards animal workers will look forward to providing it with a good shelter. “It's much better for it to recover in a home environment,” Mr. Reyes said. “It's just like a human being in a hospital so we're hoping to move it.” He added, “Little by little we're getting there. We're hoping that under the treatment and with rest, it'll be able to recover quickly.”

    It was not immediately clear how the cat got into the container.