Let fa,) and {b,} be sequences of real numbers defined as aj = l and for n21, 2a a then an41an +(-1)"27", b, = a) la,) converges to zero and {b,} is a cauchy se

Let fa,) and {b,} be sequences of real numbers defined as aj = l and for n21, 2a a Then an41an +(-1)"27", b, = A) la,) converges to zero and {b,} is a Cauchy sequence B) a,} converges to a non-zero number and (b,) is a Cauchy sequence C) 1a, converges to zero and {b,} is not a convergent sequence D) t2,)converges to a non-zero number and {b,} is not a convergent sequence