This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to do a forest bath
Set aside the time necessary for this therapeutic exercise.
For a single forest bathing session, set aside two to four hours for an excursion that is at least a half-mile long. Keep in mind that this extended time frame involves several stops for becoming aware of your senses, moments of sitting still, and mindful immersion.

Available options:
[a]. You need to recognize every shimmer, aroma, sound, and temperature in your environment, and always set aside at least one hour for this exercise. Carefully note everything or everything about this place..
[b]. This is the importance of this stretching exercise, as you cannot travel that distance without taking deep breaths. Make sure that you are comfortable with it and thoroughly clean all surfaces of all objects such as the changing water, soap and body colors of the water..
[c]. The time frame may be increased, but two consistent hours of exposure to this outdoor therapy environment will maximize noticeable improvements to mood and overall health. It is important to note that like any other therapeutic exercise, forest-bathing will require multiple sessions..
[d]. Know what to do in this gentle cleanse. Take a first step into the water to ensure your body is completely submerged and warm..
The answer is:
[c].