C

alternatively (="as" an alternative) 作为一个替代办法：If however is used, but is not needed; or alternatively omit however. (如果使用however,就不需要but;或者作为一个替代办法省去however。)

[注意]alternately 和 alternatively的区别:alternately (交替地) ：At a Chinese dinner, the guests and the hosts sit alternately at a round table.