Suppose V₁=＜R,+＞,V₂=＜R, ·＞,where R is the set of real numbers, +and · are respectively addition and multiplication. Let f: R→R and {(x) = 10x, which of the following propositions is true ( )

A．f is an injective homomorphism from V₁ to V₂

B．f is a surjective homomorphism from V₁ to V₂

C．f is an isomorphism from V₁ to V₂

D．none of the above

承包商要求对原工程进行变更的说法中正确的是( )。

A．在承包方施工中不得随意对原工程设计进行变更

B．承包方在施工中提出更改施工组织设计须经工程师同意，延误的工期不予顺延

C．承包商在施工中提出对原材料、设备的换用不需经工程师同意，由此发生的费用由承包方承担

D．工程师采用承包方合理化建议所发生的费用和获得的利益，发包方和承包方另行约定分担或分享