In a pipe closed at one end, air column is vibrating in its third...

For a pipe closed at one end, the fundamental mode (zeroth overtone) corresponds to $1$ node and $1$ antinode.

The $p$-th overtone corresponds to the $(2p+1)$-th harmonic, and the number of nodes and antinodes in the $p$-th overtone is $p+1$.

For the third overtone, $p=3$.

Number of nodes $= 3 + 1 = 4$

Number of antinodes $= 3 + 1 = 4$

Thus, the air column has four nodes and four antinodes.

Answer: four nodes and four antinodes