There are 14 elements in the actinoid series. Which of the following elements does not belong to this series?

1. U

2. Np

3. Tm

4. Fm

Hint: Tm is thulium
The elements in actinoid series is as folllows:
  Actinium(Ac),  Thorium(Th), Protactinium(Pa), Uranium(U), Neptunium(Np), Plutonium(Pu), Americium (Am), Curium(Cm), Berkelium(Bk), Californium(Cf), Einstenium(Es), Fermium(Fm), Mendelevium(Md), Nobelium(No), and Lawrencium(Lr).

Tm(Z = 69)do not belong to the actinoid series. The actinoid series is with atomic numbers 89 to 103. Thulium (Tm) has atomic number 69 belongs to lanthanoids (4f series).