Good locks on all outside and first floor windows are essential to a home's security and w

ill go a long way toward discouraging burglars. But an added protective device that is increasingly being used in homes is the burglar system, which sounds a loud bell, horn, or siren(警报器) when someone tries to break in. Although this will not always prevent entry by a determined professional burglar, it is often enough to scare off vandals(故意破坏他人财物者) and spurn-of-the- moment thieves who account for a high percentage of residential break-ins.

Security alarm systems have been available for many years and have long been common in commercial and industrial establishments and in large homes. But until the last few years, these systems were almost always professionally installed because they required complicated wiring techniques, individualized design, and sometimes lots of carpentry, all of which made them expensive.

To answer the demand for low-cost alarm systems that can be easily installed, several companies now make alarms that are specifically designed for do-it-yourselfers. These systems come with detailed installation instructions and usually do not require inside-the-wall wiring.

Which of the following statements is supported by the passage？

A．Do-it-yourself burglar systems are not as effective as those professionally installed.

B．Burglars alarm systems for home use have just recently been made available.

C．There are more burglar alarm systems in homes today than there were a few years ago.

D．Burglar alarm systems for the home will not prevent entry by a professional burglar.