Read the following the passage carefully and fill in the blanks with the proper words from the list: A. simplification B. together C.single D. combine E. trend F. alloy G. crankcase H. construction I. origins G.rigid It has long since been established practice to (1) the cylinder block and crankcase into a ( 2) unit, this generally bèing termed "monobloc" construction. The historical (3) of this form of construction date back to the early 1920s, when there was a general (4)towards (5 ) of the engine structure. Until then the cylinder block and(6) were produced as separate units, in cast iron and aluminum ( 7) respectively, and then bolted (8 ). In relation to modem engine design, the monobloc (9) provides a very necessary (10 ) foundation for the engine and reduces manufacturing costs.