One of the lyrics is
You can tell he means it by the look on his face
This is English expression. A less expressive lyricist might say:
You know he means it because (of) the look on his face
So I tried these translations:
- 你能确定。。。 因为。。。
- You can determine... because...
- 。。。 就你能确定。。。
- ... so you know that...
For "can tell" I tried 你能确定 。。。 or 你确定
For "by" I tried either 就。。。 or 因为。But 因为 seems like it's causal. Like "the look on his face is why he is serious". It's the opposite. The look on his face is effect, not cause of his seriousness. The look on his face may be the cause of your knowing he is serious.
For the full sentence I tried:
你看他脸色, 就确定 他是认真的
How would you translate that line? Emphasis on the Chinese translation for "You can tell ... by ... "
Other English ways it's used :
- "You can tell the spaghetti is cooked when it sticks to a wall."
- "You can tell he's rich by the clothes he's wearing"
- "How do you know?" "I can just tell!"