The correct options are
A U-238 is the most abundant isotope of Uranium
B U-238 is more stable than the U-235
C U-236 is not found in nature due to high instability
D U-235 is majorly used as the nuclear fuel
We discussed certain facts or better say information about the isotopes of Uranium, considering its fission as our central example to understand the chain reaction.
U-238 is the most stable isotope of Uranium and is also most abundant. Also, it may absorb a neutron with energy 1 to 100 eVs and become U-239 which on two successive beta decays becomes Pu-239 which again can absorb a neutron to become Pu-240 which is again highly unstable and undergoes spontaneous fission.
U-236 is the most unstable isotope of Uranium and due to this reason undergoes fission as soon as it is formed and hence is not formed in nature.
Due to the above reason, U-235 isotope is used as the nuclear fuel as it can absorb a slow neutron to become U-236 and hence can achieve fission.