1. 题干: A description of the substance responsible for the red colouration of leaves. (C10-T3-R2 T15)
原文: The source of the red is widely known.
Substance responsible for the red colouration --- the source of the red
2. 题干：The reason why trees drop their leaves in autumn. (C10-T3-R2 T15)
原文： the tree saves its precious resources and discards them.
drop --- discards
3. 题干：A suggestion that the red colouration in leaves could serve as a warning signal.
原文：they might act as a chemical defence against attacks by insects or fungi.
Serve as a warning signal --- act as a chemical defence
4. 题干：The most vividly coloured red leaves are found on the side of the tree facing the 19 __________ . (C10-T3-R2 T19)
原文：the most reddest are those on the side of the tree which gets most sun.
The most vividly coloured red --- the most reddest
5. 题干： The 20 _________ surface of leaves contain the most red pigment. (C10-T3-R2 T20)
原文：Not only that, but the red is brighter on the upper side of the leaf.
Contain the most red pigment --- the red is brighter
Surface --- side
6. 题干： Red leaves are most abundant when daytime weather conditions are 21_________ and sunny. (C10-T3-R2 T21)
原文：It has also been recognized for decades that the best conditions for intense red colours are dry, sunny days and cool nights, conditions that nicely match those that make leaves susceptible to excess light.
Most abundant --- intense red colours
Daytime --- days
7. 题干：The intensity of the red colour of leaves increases as you go further 22__________ . (C10-T3-R2 T22)
原文：And finally, trees such as maples usually get much redder the more north you travel in the northern hemisphere.
The intensity of the red colour of leaves increases --- get much redder
Go further --- the more north you travel
8. 题干：It’s likely that the red pigments help to protect the leaf from freezing temperature. (C10-T3-R2 T23)
原文: they might attract fruit-eating birds or increase a leaf`s tolerance to freezing.
Protect the leaf from freezing temperature
--- increase a leaf`s tolerance to freezing.
9. 题干：The ‘light screen’ hypothesis would initially seem to contradict what is known about chlorophyll. (C10-T3-R2 T24)
原文：It sounds paradoxical because the idea behind this hypothesis is that the red pigment is made in autumn leaves to protect chlorophyll, the light-absorbing chemical, from too much light.
Seem to contradict --- it sounds paradoxical
10. 题干：Leaves which turn colours other than red are more likely to be damaged by sunlight. (C10-T3-R2 T25)
原文：What is still not fully understood, however, is why some tress resort to producing red pigments while others don’t bother, and simply reveal their orange or yellow hues. Do these trees have other means at their disposal to prevent overexposure to light in autumn? Their story, though not as spectacular to the eye, will surely turn out to be as subtle and as complex.
Turn colours other than red --- simply reveal their orange or yellow hues.
To be damaged by sunlight --- overexposure to light
11. 题干：How leaves turn orange and yellow in autumn. (C10-T3-R2 T26)
原文：This unmasking explains the autumn colours of yellow and orange, but not the brilliant reds and purples of tress such as maple or sumac.
Turn orange and yellow in autumn --- the autumn colours of yellow and orange
12. 题干：How herbivorous insects choose which trees to lay their eggs in. (C10-T3-R2 T26)
原文：If insects paid attention to such advertisements, they might be promoted to lay their eggs on a duller, and presumably less resistant host.
How herbivorous insects choose --- if insects paid attention to such advertisements