Based on the following statement:

'Reported shortages of materials and labour could slow the pace at which this pipeline (housing construction) is worked through...'. With regard to the housing market, shortages of raw materials tend to put

a) leftward pressure on the supply curve thus raising prices

b) rightward pressure on the supply curve thus lowering prices

c) leftward pressure on the demand curve thus lowering prices

d) rightward pressure on the demand curve thus raising prices