单选题 Softening point of petroleum asphalt The height at which the steel ball sinks is ( ).

单选题 The higher the softening point of petroleum asphalt, ( ).

单选题 When measuring mechanical impurities in the oil product, dry the filter paper with precipitation in the oven for no less than 1 h, and then place it in the dryer to cool ( ).

单选题 The thermometer used to determine the softening point of asphalt has a measuring range of 30 to 180 ℃, and its minimum division value should be ( ).

单选题 When measuring mechanical impurities in oil products, use the precision requirements of the analytical balance ( ).

单选题 GB/ T511-88 "Method for Determination of Mechanical Impurities in Petroleum Products and Additives" the filter paper specification for use is ( ).

单选题 To measure the mechanical impurities of an oil whose 100 ℃ viscosity is less than 20 mm2/s, it is necessary to weigh the ( ) sample for experiment.

单选题 The ( ) of petroleum asphalt has nothing to do with its softening point.