单项选择题

Decide which of the choices given below would best complete the passage if inserted in the corresponding blanks. Mark the best choice for each blank on your answer sheet.
A recent educational experiment showed that the difference between "gifted" children and regular ones may have as much to do with (31) as with intelligence. An elementary schoolteacher was (32) into thinking that her students were above average in intelligence. She then (33) to get them to do outstanding work, even though their true IQs were well (34) the normal range. It seems that her belief (30) her students’ intelligence was enough to turn them (36) better learners.
It’s difficult to (37) exactly how such beliefs are expressed. It (38) have to do with (39) a teacher talks to the class: many positive, supportive expressions and few expressions of impatience, annoyance, or (40) . Non-verbal communication, including (41) expressions, probably (42) a role too. But one thing is clear: Labels and expectations (43) influence results.
Outside of the classroom, labeling can, as (44) as not, have a negative effect. The labels we put on different social groups are usually not (45) . In fact, they are often sexist or racist. Of (46) , there is good and bad in all kinds of people. But we (47) to accept some ideas about certain groups more readily than about others. The school experiment shows that such labels have a (48) deal of power. But when labels are unfair and (49) they can be very (50) .