Sara kept the secret to ________ and nobody knew aboutit.

Though this question is very difficult，if you ________ trying you willfind the right answer.

Of the seven days in a week, Saturday is said to bethe most popular _______ for a wedding in somecountries.

Mr. Smith lives __ in the mountain, but he never feels _____

28 It is only when agriculture is fully developed___________industry can have abundant materials and markets