3
Read the text. Then choose the correct answer to questions 29-31.
Rubber
trees are tapped - that is, cuts are made in the bark so that the latex, a milk-like Juice,
containing about 30-40% rubber, can be obtained. The latex is then processed by exposing it to
heat and wood smoke, or
by mechanical means, so as to separate the rubber from the 'water,
mineral salts, sugars, resins and protein matters. The rubber obtained in this way is known as,
'crude' - latex is extensively used in industry for making foam rubber, products. footwear, dolls
etc. Untreated crude rubber is naturally soft and lacks the required strength for making into
manufactured articles. To improve
its strength and usefulness, it is vulcanised, or heated with
sulphur, and the proportion of sulphur used determines the hardness and elasticity of, the
rubber.
29. From its description, we can say that latex………… .
A)is a hard substance similar
to rubber
B)must be a fairly thin, white liquid
C)is almost entirely pure rubber
D)is a by-product of
rubber
30. It~s stated in the passage that untreated crude rubber is not used in industry, because…….. .
A)its content of sulphur carries a nasty odour
B)its milky colour is undesirable
C)it lacks any kind of elasticity
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