These new ideas which need sound fine.
A. trying on
B. trying out
C. to try on
D. to try out
网友回答
A. trying on
(答案→)B. trying out
C. to try on
D. to try out
解析：句意：这些需要试验的想法听起来很好。首先区分词组：try on“试穿”，try out“尝试，试验”，所以排除AC，另外表示“需要被...”，用need doing或need to be done，所以选B。