Which of the following pairs of method invocations could NEVER be executing at the same

time? (Choose all that apply.)

A. x.a() in thread1, and x.a() in thread2

B. x.a() in thread1, and x.b() in thread2

C. x.a() in thread1, and y.a() in thread2

D. x.a() in thread1, and y.b() in thread2

E. x.b() in thread1, and x.a() in thread2

F. x.b() in thread1, and x.b() in thread2

G. x.b() in thread1, and y.a() in thread2

H. x.b() in thread1, and y.b() in thread2

The answer in K& B Self

test book is bit confusing(Page 754).