B. how plants and tree roots share water

C. vegetables grow better in partial shade

D. how leaves gain sunshine under the tree

31.The underlined words “leaf hoppers” in Para five may be a kind of ______.

A. plans

B. pesticides

C. insects

D. potatoes

D

It is always the same minority of top pupils, usually sitting in the front, who raise their hands to answer questions, while the majority switch off. This deep-seated classroom habit is widening the achievement gap in our schools, according to the education expert Dylan William.

Some sort of randomization process is required, William long ago decided, and his unusual solution is to write the pupil’s names down on lollipop（棒棒糖）sticks, the teacher then pulling them at random from a pot. No one can hide---everyone is potentially in the firing line.

Over the course of one summer term, he put the idea into practice on a mixed-ability class of 12- to 13-year-olds at a school in Borehamwood. The aim was to involve every pupil in the lesson.

A further innovation---small, hand-held whiteboards for each student---came as a direct result of an unforeseen problem with the lollipop sticks.

Unable to show off their brilliance in the front of the class, the regular hands-up group were getting frustrated, and had even started to become disruptive（捣乱的）. “The high-achieving girls were really struggling,” William says. “They’re used to putting their hands up only when they know the answer. The random lollipop method was putting some of the high achievers into the unacc ustomed position of sometimes not knowing the answer.”