________ about wild plants that they decided to make a trip to Madagascar for further research.

A.So curious the couple was

B.So curious were the couple

C.How curious the couple were

D.The couple was such curious

答案及解析： B

解析：

句意：这对夫妇对野生植物如此好奇以至于他们决定去马达加斯加旅游以便进一步研究。The couple指两个人，因此谓语动词要用were，因此排除A、D两项；题干中含that引导的结果状语从句，故设空处用“so+curious”，与后面的that从句构成“so…that…”句式，so curious放在句首，后面主句谓语动词需部分倒装。