Questions 10-15

　Four couples, the Bascos, the Jeffersons, the Pardas, and the Roberts, are learning a new dance. The dancers must perform this dance in pairs. At the beginning of the dance, each of the married couples is such a pair, but there are three calls for partner changes-calls X, Y, and Z-with the following results:

    When call X is made, Mr. Basco and Mr. Parda exchange partners.

    When call Y is made, Mrs. Roberts and Mrs. Jefferson exchange partners.

    When call Z is make, Mr. Jefferson and Mr. Parda exchange partners.

    When more than one call is made, each change of partners is based on the arrangement of partners produced by the preceding call. *

    10. If, since beginning of the dance, there has been one partner change, made in response to call X, which of the following must be a pair of partners?

    (A) Mr. Basco and Mrs. Parda

    (B) Mr. Basco and Mrs. Roberts

    (C) Mr. Jefferson and Mrs. Parda

    (D) Mr. Jefferson and Mrs. Basco

    (E) Mr. Roberts and Mrs. Jefferson

    11. If, after the first two calls of the dance, each dancer is again partnered with his or her own spouse, the calls made could have been

    (A) X followed by Y

    (B) Z followed by X

    (C) X followed by X, or Y followed by Y, or Z followed by Z

    (D) X followed by X, or Y followed by Y, but not Z followed by Z

    (E) X followed by X, or Z followed by Z, but not Y followed by Y

    12. If, since the beginning of the dance, two partner changes have been made, the first in response to call X and the second in response to call Y, which of the following must be true?

    (A) Mrs. Basco is partnered with Mr. Roberts.

    (B) Mrs. Jefferson is partnered with Mr. Jefferson.

    (C) Mr. Parda is partnered with Mrs. Roberts.

    (D) Only two of the women are partnered with their husbands.

    (E) No man is partnered with his wife.

    13. If Mr. Basco is partnered with Mrs. Basco after the first two calls of the dance, and if the second call was Y, which of the following is true of the first call?

    (A) It must have been X.

    (B) It must have been Y.

    (C) It must have been Z

    (D) It could have been any of the three calls except X.

    (E) It could have been any of the three calls except Z.

    14. If Mr. Jefferson is partnered with Mrs. Basco after the first two calls of the dance, and if the second call was Z, which of the following is true of the first call?

    (A) It must have been X.

    (B) It must have been Y.

    (C) It must have been Z.

    (D) It could have been any of the three calls except Y.

    (E) IT could have been any of the three calls except Z.

    15. If the dance begins with the three calls Z, X, and Y, in the order given, it must be true that after the third call.

    (A) Mr. Parda partners Mrs. Jefferson

    (B) Mr. Parda partners Mrs. Roberts

    (C) Mr. Basco partners Mrs. Basco

    (D) Mr. Basco partners Mrs. Jefferson

    (E) Mr. Basco partners Mrs. Roberts