Answer: B. Prepare a laser rangefinder.
Answer analysis: When discussing the preparations that need to be done before applying site surveys, we need to consider how these preparations can help the site survey go smoothly and the subsequent work to be carried out effectively. Now, let's analyze each option one by one:
A. Prepare a ladder: Although a ladder may be useful in certain specific site surveys, such as when you need to check the situation at a high place, it is not necessary for every site survey. In addition, carrying and using a ladder may also bring certain safety risks, so it should not be considered as a necessary preparation before going to a site survey.
B. Prepare a laser rangefinder: A laser rangefinder is an instrument that can accurately measure distances and is very useful for site surveys. It can help us quickly and accurately obtain information such as the spatial dimensions and layout of the site, providing an important basis for subsequent design, planning and other work. Therefore, this option is reasonable.
C. Prepare a notebook and pen: Although notebooks and pens are traditional tools for recording information, they may not be the most efficient way to record information in today's increasingly advanced modern technology. In addition, if the on-site environment is complex or a large amount of information needs to be recorded, handwritten records may seem inadequate. Of course, in certain specific situations, such as when electronic devices cannot be used or handwritten signatures are required, notebooks and pens are still necessary. But in the context of this question, they are not the primary preparation before going to the site survey.
D. Prepare product brochures: Product brochures are mainly used to display product information and attract potential customers, and have no direct connection with the preparation work for site surveys. During the survey process, product brochures may not play a substantial role, so this option can be excluded.
In summary, before applying site surveys, the most important preparation is to prepare a laser rangefinder. This tool can help us quickly and accurately obtain key information on the site and provide strong support for subsequent work.
Therefore, the correct answer is B: "Prepare a laser rangefinder".