Q1: Which of the following pairs is not correctly matched ?

ANS:A - Uranium - 233 : Fertile material.

Uranium-233 (U-233) is indeed a fertile material. In nuclear engineering, the term "fertile" refers to isotopes that can undergo nuclear reactions to produce fissile isotopes when they capture neutrons. In the case of U-233, it can absorb a neutron and undergo a series of nuclear reactions, ultimately transmuting into fissile isotopes such as uranium-235 (U-235) or plutonium-239 (Pu-239). This process is known as neutron capture and subsequent radioactive decay. Uranium-233 is not naturally occurring but can be produced artificially. It is typically obtained by irradiating thorium-232 (Th-232) with neutrons in a nuclear reactor. Th-232 is a fertile material itself, and when it absorbs a neutron, it can be converted into U-233, which can then be used as a nuclear fuel in reactors. Therefore, Uranium-233 is indeed classified as a fertile material due to its ability to undergo nuclear reactions and produce fissile isotopes upon neutron capture.