慢性阻塞性肺病的原发性原因是烟草烟雾(包括二手烟或被动接触)。

The primary cause of COPD is tobacco smoke (including second-hand or passive exposure). Other risk factors include.

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慢性阻塞性肺病的原发性原因是烟草烟雾（通过烟草使用或二手烟雾）。

The primary cause of COPD is tobacco smoke (through tobacco use or second-hand smoke).

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但研究表明，大部分不孕症的原因是由男方或女方生殖系统的病变所引起的，心理因素很少成为原发性病因。

But research shows that most infertility is the result of physical problems in a man's or woman's reproductive system, and psychological factors are rarely the primary cause.

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