A pilot with a lazy yellow flame would indicate what?

A pilot flame that is lazy and yellow typically indicates an issue with the air-to-fuel ratio being out of balance. Specifically, a lazy yellow flame suggests that there is an excess of fuel in relation to the available air for combustion. This condition often occurs when the orifice size is too large, allowing more gas to flow than can be properly mixed with air.

When the orifice is too large, there's not enough air to facilitate complete combustion of the gas, leading to an inefficient burn characterized by a yellow, flickering flame. In contrast, a well-adjusted pilot flame should be blue and steady, indicating proper mixing of gas and air, and complete combustion.

The other options relate to different gas pressure conditions or orifice sizes that would affect the combustion process differently, but in the case of a lazy yellow flame specifically, the most direct cause is that the orifice size is too large for the system's intended operation. Thus, a larger orifice creates an imbalance leading to incomplete combustion and the corresponding flame characteristics.