A mixture of Krypton and Xenon is used in photographer's flash tube for taking high speed pictures
Correct B

The image above shows the flashtube of a typical camera. A flashtube, also called a flashlamp, is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for very short durations. Flashtubes are made of a length of glass tubing with electrodes at either end and are filled with a gas that, when triggered, ionizes and conducts a high voltage pulse to produce the light. Flashtubes are used mostly for photographic purposes but are also employed in scientific, medical, industrial, and entertainment applications.

As with all ionized gases, xenon flashtubes emit light in various spectral lines. This is the same phenomenon that gives neon signs their characteristic color. Due to its high-efficient, white output, xenon is used extensively for photographic applications, despite its great expense. Krypton is also used in photographic flash tubes and can be as good as 40% efficient, but requires up to a 70% increase in pressure over xenon to achieve a more efficient flash.