Which of the following statements is (are) true ( ) Ⅰ. The number of cyclic subgroups of the additive group of integers is infinite Ⅱ. The number of cyclic subgroups of the additive group of real numbers is infinite
A．Ⅰ and Ⅱ
B．Ⅰ only
C．Ⅱ only
D．neither Questions 43、44 refer to the space requirements of different methods of storing graph The Choices for these questions are combinations of the following statement Ⅰ. The space required depends on the number of vertices Ⅱ. The space required depends on the number of edges