Step 1: Understand the task.
Vocational guidance steers a person toward a suitable career. We must pick which of the four factors $J, K, L, M$ it relies on.
Step 2: Weigh Capacities (J).
A person's abilities and skills decide whether they can perform a job, so this factor is clearly needed.
Step 3: Weigh Attitudes (K).
Interests and motivation decide job satisfaction and staying power, so this factor matters too.
Step 4: Weigh Available opportunities (L).
A career choice must match real job-market demand, otherwise the guidance is unrealistic. So this is essential.
Step 5: Weigh Personal resources (M).
Money, family support, and access to training decide what paths are actually feasible, so this counts as well.
Step 6: Combine the findings.
Internal factors $(J, K)$ and external factors $(L, M)$ are all required, so every option belongs.
\[ J + K + L + M = \text{all four} \]
Step 7: Conclude.
Hence all four factors guide the choice.
\[ \boxed{\text{C. J, K, L and M}} \]