tell me at once
1.马上告诉我
can you tell me at once
1.你能马上告诉我吗
2.你能立刻告诉我吗
3.一般疑问句
you may as well tell me the truth at once
1.你还不如把实话马上告诉我吧
2.你还不如把实话告诉我吧