One of the major criticisms of humanistic therapies is that a. They are too imprecise and unstructured. b. They treat only the symptom of the problem. c. The therapist dominates the patient-therapist interaction. d. They work well only on clients of lower socioeconomic status.

Begin by understanding what humanistic therapies entail. Humanistic therapies focus on self-development, growth and responsibilities. They seek to help individuals recognize their strengths, creativity and choice in the 'here and now'.

Now, using the understanding of humanistic therapies from Step 1, each option can be assessed for validity. Here, it is necessary to compare the features of humanistic therapies with the statements provided in the options.

After analyzing the given options, it's clear that the statement 'They are too imprecise and unstructured' aligns with the criticism that humanistic therapies can be less structured and systematic than other therapeutic approaches. Hence, the correct option is 'a'. Other options do not accurately represent the typical criticisms of humanistic therapies. Option 'b' is incorrect because humanistic therapies aim to treat the cause and not just the symptoms. Option 'c' is also incorrect as humanistic therapies allow for a more equal relationship where the client's input is highly important. Lastly, option 'd' is inaccurate because humanistic therapies are not limited by socioeconomic conditions but rather revolve around the client's personal conditions and experiences.