The direct reason for specialisation is ______.

A．Last month, one 4 years old ape managed to say something through a synthesizer.
B．"Bacteria should have rights" is a ludicrous statement.
C．All gorillas are suing for their constitutional rights.
D．No one cares about animal rights, in fact.

A．it is ridiculous to think about cockroach liberation seriously
B．the law's denial of rights to animals is a matter of bias-speciesism
C．apes can express feelings accurately through synthesizer
D．gorillas should be declared to be persons under the constitution