93年2月GRE试题.docVIP

93年2月GRE试题 SECTION 2 Questions 1-6 A plant grower pollinates female holly plants with pollen from male holly plants. The grower has exactly six strains of holly plants-S, T, W, X, Y, and Z— available for use in pollination. Male and female speci- mens of each strain are available. A pollination grouping consists of at least two holly plants, one male and one female. For any pollination grouping, the grower can use a male of any of the six strains to pollinate a female of any of the six strains, as long as the following restric- tions are not violated: 　An S female plant can be pollinated only by an S male plant. 　A T female plant can be pollinated only by a Z male plant. 　An X female plant can be pollinated by neither a T male plant nor an X male plant. 　In any single pollination grouping containing a Z female plant that is pollinated by a T male plant, there must also be an X female plant that is pollinated by a Z male plant. 1. Which of the following lists two pairs of acceptable pollinations in a single complete grouping? 　First Pair 　Second Pair Female　Male Female　Male (A) S S W S (B) S W W W (C) T Y Z Z (D) X X Z X (E) X Y Z T 2. The grower can use a Z male plant to pollinate a female plant of any of the following strains EXCEPT (A) S (B) T (C) W (D) Y (E) Z 3. The grower can choose to pollinate an X female plant from a total of how many different strains of male plants? (A) One (B) Two (C) Three (D) Four (E) Five 4. Which of the following is a complete and accurate list of the strains whose female plants can be selected by the grower for pollination by a W male plant? (A) T, W, X, Y, Z (B) W, X, Y. Z (C) W, Y, Z (D) Y, Z (E) Z 5. If the grower decides not to use Z male plants, which of the following is a possible pollination pairing? Female Male (A) S W (B) T Y (C) X T (D) Z T (E) Z