The back garden of our house contains a lawn ，____very pleasant to sit on in summer.
A
「句意」我家的后花园有一片草坪，夏天坐在上面会令你心旷神怡。
「难点」which引出非限制性定语从句，在句中作主语，且和siton构成动宾关系。类似的句子有：Thisroomiscomfortabletolivein这句中livein和thisroom构成动宾关系。
Allofuswouldhaveenjoyedthepartymuchmoreifthere_____quitesuchacrowdofpeoplethere.
Itisimperativethatstudents_____theirtermpapersontime.
_____ifIhadarrivedyesterdaywithoutlettingyouknowbeforehand.