The tone of this passage is ______.

A．security alarm systems were not safe at all
B．security alarm systems were easy to break down
C．security alarm systems were not available
D．security alarm systems required complicated wiring techniques, individualized design, and sometimes lots of carpentry

A．good locks are essential to home's security
B．there are many types of security alarm systems for the home
C．an ounce of prevention is worth a pound of cure
D．there are burglar alarm systems that can be installed without professional help