B) Explain the words in bold from the text and make up sentences of your own. Use English-English dictionaries to help you

Timber, as a natural product, is rarely free from blemishes or defects. Timber imperfections 1) _____: natural, conversion and seasoning defects, according to whether they were present in the living tree, or arose during subsequent processing. Additionally, timber may be subjected to deterioration by weathering, fungal and insect attack and fire.

On prolonged exposure to sunlight, wind and rain, 2) _____ their natural colours and turn grey. Sunlight and oxygen break down some of the cellulose and lignin into water-soluble materials which are then leached out of the surface leaving it grey and denatured. Moisture movements, 3) _____, raise the surface grain, open up surface checks and cracks and increase the risk of subsequent fungal decay. Provided the weathering is superficial, the original appearance of the timber can be recovered by removing the denatured surface.

Wood preservatives contain pesticides in the form of insecticides and fungicides. Their use is therefore strictly controlled 4) _____ environmental damage.

Timber is an organic material and therefore combustible. Surface treatments, 5) _____, include antimony trioxide flame-retardant paints which are suitable for both interior and exterior use. Intumescent coatings, which swell up and char in fire, are suitable for most environments if overcoating is applied. However, 6) _____ may be negated by unsuitable covering or removal by redecoration.

a) associated with repeated wetting and drying cycles;

b) to limit unnecessary or accidental;

c) which cause the evolution of non-combustible gases in fire;

d) the protection afforded by surface treatments;

e) can be divided into three main categories;

f) external timbers gradually lose.