If you are walking away from a clock tower ，you will hear the ticking of the clock fade to a point ________ it cannot be heard.
C
译文：如果你从钟塔旁走过.你将会听到滴答声，直到你走远。此题考查定语从句。where在定语从句中做地点状语，先行词是apoint。
Childrenhaveanatural________abouttheworldaroundthem.
Well-arrangedsentencesareconsideredgrammaticalsentencesthatareformedfollowingasetofsyntacticrules.
Thebasicunitinthestudyofmorphologyis______.