Accordingtothepassage,whatattr actsman'sgreaterattention?
A.Flyash.
B.Theconstr uctionofdams,bricks,androads.
C.Extr actingaluminum,silicon,andmagneticfromash.
D.Theavailabletechnology.
正确答案：A答案为A。根据第一段最后一句，Asaby-productofburnedcoal，flyashrequiresnoadditionalexpenditureofenergytobeproduced，whilecementproductionrequiresgreatamountsofenergy作出该项选择。
