请按句意及所给的汉语提示，写出空缺处单词的正确形式。
Can you answer the            (第三) question and the fourth one in Chinese ?
Which is              (安全的), traveling by train or by plane ?
     (吸烟) is bad for your health.
Please read the ____________(说明) carefully before you use a new product.
Work hard and you will be _______________(成功的) in the future.