What are the causes of these problems?

这些问题的原因是什么？

Scientists study the causes of the aurora.

科学家们研究极光的形成原因。

Smoking is one of the main causes of emphysema.

吸烟是导致肺气肿的主要原因之一。

Scientists are studying the causes of ageing.

科学家们在研究变老的原因。

Doctors are researching the causes of acardia.

医生们正在研究无心的成因。

Smoking is one of the main causes of lung cancer.

吸烟是导致肺癌的主要原因之一。

Smoking is one of the leading causes of emphysema.

吸烟是导致肺气肿的主要原因之一。

Scientists are studying the causes of moonquake.

科学家们正在研究月震的成因。

Stress and anxiety are common causes of insomnia.

压力和焦虑是失眠的常见原因。

Doctors are studying the causes of this morbidity.

医生们正在研究这种病态的原因。