bǎo xiǎn
这样做可不保险。
Zhèyàng zuò kě bù bǎoxiǎn.
Doing it this way is not safe/reliable.
你按我说的办，保险不会出错。
Nǐ àn wǒ shuō de bàn, bǎoxiǎn bù huì chūcuò.
If you do as I say, you surely won't make a mistake.
他这个时候还没来，保险是误了车了。
Tā zhège shíhou hái méi lái, bǎoxiǎn shì wù le chē le.
He hasn't come yet at this time, he must have missed the bus.