For constructing a terrazo floor. Pick up the incorrect statement from the following :

• a base course is prepared as in cement concrete flooring
• a 32 mm thick layer of cement concrete (1 : 2 : 4) is laid on the base course and the surface is made smooth by trowelling
• glass strips are driven into the layer according to the pattern required
• after final grinding is over, oxalic acid mixed with water is spread over and rubbed hard with soft material
• none of these.