In the given question we have to use the concept of wavelength. Hence, following will be the correct answer. The distance between successive crests or trough in a wave of a wave. It is Velocity divided by the frequency.

A node is actually the point along the standing wave where the wave has the minimum amplitude. For instance, in the vibrating guitar string, ends of a string are the nodes. The opposite of a node is called an anti-node, a point where amplitude of standing wave is at the maximum. These occur midway between nodes.

An anti-node is actually the point along the standing wave where the wave has the maximum amplitude.. The opposite of an anti-node is called a node, a point where amplitude of standing wave is at the minimum. These occur midway between anti-nodes.