Correct among the following

1) All transition elements are d-block elements

2) All d-block elements are transition elements

3) Helium is an inert gas

4) Aluminium is a representative element

Elements in which the last electron enters the d-orbitals, are called d-block elements.

Those elements which either themselves or their ions have incomplete filled d-orbitals are called transition elements. Those elements that have filled d-orbitals in their ground state or in the form of ion, cannot show the properties of transition elements. 

For example: Zinc is a d-block element but not a transition elements because of having filled d-orbital. Hence statement (1) is true but (2) is false.

Now, Helium is an inert gas as it has a completely filled outer shell and it belongs to group 18 of the periodic table. Hence statement (3) is true.

Elements present in s and p-block elements except noble gases are known as representative elements and Aluminum belongs to the p-block hence it is a representative element. Hence statement (4) is also true.

Therefore, option (b) is correct.