Suppose that machine M$1$ recognizes abc exactly, and machine M$2$ recognizes bcb exactly. Further suppose that machines M$1$ and M$2$ are put into a larger machine, M$.$ M$1$ has states s$1,$ s$2,...$ s$5,$ and M$2$ has states t$1,$ t$2,...,$ t$7.$ Because these inputs are given to M$,$ they are duplicated and passed to M$1$ and M$2.$ Finally, if either M$1$ or M$2$ accepts the input, one will say that M accepts the input.

Which of the following strings is accepted by M$?$

abbccb

abcbc

abcbcb

abc