The momentary supply of wheat has an elasticity of supply equal to the short-run supply of wheat has an elasticity of supply equal to

The short-run supply of wheat has an elasticity of supply equal more than zero but less than infinity. If ever the farmers already have a crop which is ready to harvest, they have the right to choose to harvest if the price is high, or harvest a smaller amount if the price is low. So the elasticity of supply is more than zero but less than infinity.
The momentary supply of wheat is perfectly inelastic. The quantity that is supplied is depending on the crop-planting decisions made earlier, so the elasticity of supply is zero.