我们要埋头苦干。我们肩上的担子重，责任大啊！

A、We must immerse ourselves in hard work, we have difficult task to accomplish and bear a heavy responsibility on our shoulder.
B、We must immerse ourselves in hard work; we feel a heavy burden on our shoulder and bear a heavy responsibility.
C、We must immerse ourselves in hard work, we have difficult task on our shoulder and bear a heavy responsibility.
D、We must immerse ourselves in hard work; we have difficult task to accomplish and a heavy responsibility to bear.