I will add a few things to @ucbalumnus very comprehensive post. The Cal States and UC’s only use 10-11th grades to calculate their GPA: https://rogerhub.com/gpa-calculator-uc/
The exception is Cal Poly SLO which does include 9th grades also.
The Cal States (except SLO) also base their admissions on the Eligibility index (EI). Each applicant is ranked based on major and EI and accepted from the top down until all spots are filled.
(CSU/UC GPA x800) + (SAT Math+CR) or ( CSU GPA x200) + (ACT composite x10)
A high SAT/ACT score can make up for a less than stellar GPA.
Impacted campuses and majors will be definitely more selective than non-impacted campuses and majors. Here is a link to impacted majors for the Cal States and campuses:
https://www.calstate.edu/sas/documents/impactedprogramsmatrix.pdf
Cal Poly SLO is a viable option for B students but will depend upon major. Some majors have over a 50% acceptance rate or higher such as Dairy Science, Plant Science, Recreation Admin, Bioresource and Agricultural Engineering, Agribusiness, Ethnic studies and Philosophy to name a few.
For the UC’s, the minimum UC GPA required to apply is 3.0 for in-state applicants but at this level, you are looking at possibly UC Merced and will also be major dependent.
There are many options to explore.