[单项选择]The total cultivated area is 13,000 acres, （　） 10,000 acres are irrigated fields.
A. which
B. of which
C. in that
D. of that

[简答题] Popular and learned words In every cultivated language, there are two great classes of words which, taken together, comprise the whole vocabulary. First, there are those words with which we become acquainted in (47)______ conversation, which we learn, that is to say, from the members of our own family and from our familiar (48)______, and which we should know and use even if we could not read or write. They concern the common things of life, and are the stock in (49)______ of all who speak the language. Such words may be called "popular" since they belong to the people at large and are not the (50)______ possession of a limited class. On the other hand, our language includes a multitude (大量的) of words which are (51)______ seldom used in ordinary conversation. Their meanings are known to every educated person, but there is little occasion to (52)______ them at home or in the market-place. Our first acquaintance with them comes not from our mother’’s