The correct answer is B. Is.

1. Is: This option is correct because "all we need" refers to a singular concept (the requirement for dedicated teachers) even though "teachers" is plural. The phrase "all we need" functions as a singular subject in this context, so it takes the singular verb "is."

2. Are: This option is incorrect because it is used with plural subjects. Here, "all we need" is treated as a singular subject, so "is" is the appropriate verb form.

3. Was: This option is incorrect because it is the past tense singular form. The sentence needs the present tense, and "all we need" is singular in the present context.

4. Were: This option is incorrect because it is the past tense plural form. Again, "all we need" is singular, so "were" does not fit.

Summary:

- B. Is is the correct choice because it correctly matches the singular concept of "all we need" with the appropriate present tense form of the verb.