Step 1: Understand the types of friction.
Static friction is a self-adjusting force that adjusts according to the applied force up to its maximum limit. It increases as the applied force increases but does not exceed its maximum value, beyond which motion begins.
Step 2: Conclusion.
Thus, static friction is the self-adjusting force among the options.
Final Answer:
\[
\boxed{\text{Static friction}}
\]