Use of moist heat can control microbial growth in many circumstances, but heat-sensitive items and those susceptible to moisture cannot be sterilized in this manner. Which of the following correctly describes a method of physical control used to control microbial growth on or in such items?
a. Filtration is the passage of a liquid or a gas through a screenlike material with pores small enough to retain microorganisms. A vacuum is typically used to force the liquid through the mesh, and then the sterile liquid or gas is collected in a sterile container on the other side.
b. Nonionizing radiation, such as UV light, has a wavelength longer than that of ionizing radiation. The wavelengths of UV light are absorbed by cellular DNA in organisms directly exposed to the light.
c. Desiccation is a process that removes water from microorganisms, leaving them unable to grow or reproduce, but still viable.
d. Osmotic pressure is a process that uses high concentrations of salts and sugars to preserve food.

Non-ionizing radiation is radiation that has a lower frequency, or longer wavelength, in the EMR spectrum. These frequencies range from that of power lines, radios, and cell phones, up to visible light. Non-ionizing radiation is not powerful enough to break the chemical bonds in molecules. In general, it is not harmful to human health as radiation per se, but could be harmful in terms of the transfer of heat energy. An example of an emitter of non-ionizing radiation is a microwave oven.
Non-ionizing radiation is less harmful because the rays carry much less energy. Radio waves, light, and even heat are examples of non-ionizing radiation. For the most part, these kinds of radiation do not cause any damage. However, ultraviolet light is a kind of non-ionizing radiation that can be harmful - it can cause mutations in DNA
Non-ionizing radiation is limited to the lower energy range electromagnetic radiation, which is more commonly known as light. However, the light we can see with our eyes, visible light, is only a small section of the electromagnetic radiation spectrum as seen here
Hence the right answer is option "b"