Why (3) is not correct?isn't infrared produced? Isn't black body radiation produced?

High temperature cannot lead to emission of line spectrum.

Any object, not necessary gas, with a temperature emits electromagnetic radiation. The radiation so emitted is caused by collisions between molecules in the object, which possess thermal kinetic energy energy. By this means, the radiation is sometimes called "thermal radiation". Spectrum of such thermal radiation is a continuous one (because a molecule can lose any amount of thermal energy during a collision). Objects at room temperature emit thermal radiation that peaked in the far infra-red range and is not visible by human eyes.

However, as the temperature of an object increases, the "peak" of the thermal radiation shifts towards higher frequencies. At temperature of about 2500 ~ 3000 K (that is the temperature of a tungsten-filament light), the peak of the spectrum is within the visible range, and we can see it with our eyes.

Therefore, a gas at high temperature emits a continuous spectrum produced by drastic collisions among molecules. This is, in fact, the process that occurs on the surface of the sun. Hence, statement 3 is wrong.
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No is B