The National Autistic Society said the exact causes of autism were unknown.

英国全国孤独症协会指出，孤独症的确切成因仍然未知。

youdao

Its exact causes are unknown, but it may involve immunologic reactions.

它的确切原因不明，但它可能包括免疫反应。

youdao

However, the National Autistic Society in the UK says that the exact causes of autism were unknown.

然而，英国国家自闭症学会说自闭症的确切病因还不为人知。

youdao

Though the exact causes of breast cancer are unknown, understanding its risk factors is essential to prevention.

WHITEHOUSE: The White House