I. (Weight: 2096) what does the following code fragment do? vector my_vector; my_vector.push back(3.456) my_vector.push_back(5) double result my vectormy_vector(0] cout prev; a. node-ptr->prev->next = tail; tail->prev node_ptr->prev; b. DNode node_ptr-head head new DNode( Tamika") head->next node ptr; node_ptr->prev head DNode DNode DNode DNode DNode next prev a datas John" next prev datas "Harry next prev a next s preva datas "Sam" next s preva