答 (dá) means 'to answer, to reply', but in modern Chinese it is rarely used alone as a standalone verb; it mainly appears as a morpheme in compounds like 回答 (huídá, the standard word for 'answer') and 答应 (dāying, which can mean 'answer' but more often 'agree' or 'promise'). For everyday speech, use 回答 instead of 答 by itself.