错了, 应改成:
We must be careful , for a lion escaped from the zoo.(for补充说明原因)
/We must be careful as/since a lion escaped from the zoo.(as/since表示已知的原因)
错了, 应改成:
We must be careful , for a lion escaped from the zoo.(for补充说明原因)
/We must be careful as/since a lion escaped from the zoo.(as/since表示已知的原因)