At the outset, it seemed necessary to be on guard against the other two.

一开始，似乎有必要提防另外两个。

youdao

In the absence of a common goal or common enemy, they prefer to be on guard against each other.

在缺乏共同目标或共同敌人的情况下，他们宁愿相互防备。

youdao

When you have to deal with the local merchants, you have to be on guard against being strung along.

你在和当地的商人打交道时，你必须提防上当受骗。

youdao

Many but not all ETF strategists use backtesting, and investors who are accustomed to mutual funds, where regulations generally forbid this practice, need to be on guard against it, experts say.

WSJ: When Cheap Funds Cost Too Much

But she warned members of the public to be on their guard against the virus.

BBC: Flu rate 'at record low'

You have to be constantly on your guard against being robbed, beaten or dragged into cars by strangers.

BBC