Which of the following are correct?

a) First ionization enthalpy of He < Second ionization enthalpy of Li
b) Li has the highest second ionization enthalpy
c) All d-block elements are transition elements
d) The only alphabet not found in the periodic table is the letter ‘J’
e) Francium concentrations is ~10-18 ppm on Earth

We know that First ionisation enthalpy of $\mathrm{He}<$ Second ionisation enthalpy of $\mathrm{Li}$ because in second ionisation we have to remove an electron from Li⁺ which requires more energy as compared to He.

Hence, statement 1 is true.

And, statement 2 is also true.

Now, we know that all transition elements belong to d-block elements but all d-block elements are not transition elements.

Hence, statement 3 is false.

Now Statement 4 is also true because the  letter ' J '

Is the only alphabet not found in the periodic table.

And, Statement 5 is also true that Francium concentration is $~{10}^{-18}\mathrm{ppm}$ on Earth.

Hence, option(b) is the answer.