根据材料，回答问题。People differ in their ability to learn. They differ in the greatness of ability they have， as well as in the kind of ability they have. Some students can 11 get passing marks in high school，while others earn all A's. Certain students are successful in mathematics and science 12 do poorly in literature and history. Other students do well in literature and history and poorly in science and mathematics.It is hard to find out what causes these differences. Are they 13 to the person'sbackground， to the kind of home or neighborhood in which he 14 and the kind of experiences he had? Or is a person's ability to learn passed onto him from his ancestors.Most studies of these questions seem to point 15 the fact that both the conditions in which a person grows and the traits passed on to him from his ancestors determine how the person learns.It is true that some families have a usually large 16 of gifted members. So， these families may live in homes in which there are books and other opportunities for learning. The parents may be 17 with their children's success in school. In other families， there are generations of people with very modest abilities. In these famihes， interest in learning may not be 18 Differences between boys and girls in ability to learn have also been reported. Generally，however， the differences have been small. Girls 19 to have slightly better grades in elementary school， and they are slightly better in word skills than boys. Boys， 20， get higher scores on mathematical learning tasks and in science and mechanics. 11.（ ） 查看材料