没底

jīn nián gāo kǎo néng fǒu tōng guò tā xīn lǐ méi dǐ

今年高考能否通过，他心里没底。

He's not sure whether he can pass the national college entrance examination this year.

cóng yī kāi shǐ wǒ jiù jué de tā duì nà zhuāng hūn shì xīn lǐ méi dǐ

从一开始我就觉得她对那桩婚事心里没底。

I thought from the first that she was a little unsure about that marriage.

néng bù néng yíng wǒ xīn lǐ méi dǐ

能不能赢，我心里没底。

I'm not sure whether I can win or not.