Translation:We go to work at 9 o'clock in the morning.
Ugh, this section is incredibly frustrating...it's hard enough with the long, complex sentences with all the numbers, but the incredibly picky-ness of the translations is driving me nuts...and it's virtually every exercise that does it.
I just got marked wrong for saying 9:00 instead of 9.
As a native speaker, I generally use 早上 to mean morning, as in, the earlier morning hours, and 上午 to mean before noon, as in, the later morning hours. Depending on the time, the two terms can be used interchangeably. For example, you'd use 早上 and not 上午 if you wanted to say 6 am, but if you wanted to say 11 am, you'd use 上午 and not 早上. If you wanted to say 9 am, either 早上 or 上午 would be okay to use.
上班 means “start work”. Notice it doesn’t mean “go to work” like many here are complaining of. I guess one could already be on work premises earlier than 9 o’clock and a new coworker asks “when do we start work?”, so the answer is “we start work at 9 o’clock ...”
上课（shang ke) on the other hand, means “start school/class”.
A question to the native speakers here: may the time phrase be separated with one part being placed before the subject (e.g. for emphasis) and the remaining part after it? Like, in our sentence here. Can we say: 上午我们九点上班。And if yes, may we do so with the latter (i.e. shorter-period) part? Like, 下午你今天做什么？ Please kindly enlighten me.