汉译英：当他走进办公室时，他的朋友们手里拿着礼物，突然唱起生日歌

when he came in the office ,his friends started to sing happy birthday to him with gifts in their hands.

With presents in their hands,his friends suddenly began to sing when he walked into the office.

When he entered the office, his friends suddenly sang the song of "happy birthday", presents in hand.

As soon as he walked in the office, his colleagues started to sing the birthday song with presents in teir hands.

His friends suddenly started singing birthday song with presents in their hands when he walked into the office.

His friends bring some presents and suddenly sing the birthday song when he went into office.