I feel a bit out of form today; I'm afraid my tennis won't be up to your standard.我今天略感不适，恐怕我的网球水平达不到你的标准。

The little girl ran a temperature and had to be up to bed.那个小女孩发烧了，得让她上床躺着。Where's that naughty child now? I'm sure he'll be up to no good wherever he is.那调皮孩子哪儿去了? 我看，他到哪儿也做不出好事来。