A horizontal force on a block is increased very slowly from zero. Which statement best explains why the block initially remains at rest?
a) Static friction is zero until motion begins; only kinetic friction counters the applied push.
b) The horizontal force increases the normal reaction, producing enough friction to hold the block.
c) Static friction adjusts itself up to a limiting value equal to the applied force, keeping the block at rest.
d) Static friction remains at its maximum value μsN even for very small applied forces, balancing the push.