Arrange the following nuclei in the increasing order of their binding…

The correct answer is Option (4) → D, B, A, C

For light nuclei the binding energy per nucleon rises steeply with mass number, but ⁴He is an exception: its two protons and two neutrons form a very tightly bound, doubly closed structure, so it stands well above its neighbours on the curve.

(D) ²H: about 1.1 MeV per nucleon
(B) ³H: about 2.8 MeV per nucleon
(A) ⁶Li: about 5.3 MeV per nucleon
(C) ⁴He: about 7.1 MeV per nucleon

So the increasing order is D, B, A, C.

NCERT (2026-27):
Nuclear Binding Energy – “… Figure 13.1 is a plot of the binding energy per nucleon \( E_{bn} \) versus the mass number \( A \) for a large number of nuclei. We notice the following main features of the plot:
… (ii) \( E_{bn} \) is lower for both light nuclei ( \( A \lt 30 \) ) and heavy nuclei ( \( A \gt 170 \) ).”