The source of energy of the sun and stars is obtained from the nuclear fusion of :

1. uranium
2. thorium
3. hydrogen
4. ²³⁵₉₂U

In a nuclear reactor :

1. moderator is used to control the number of neutrons.
2. controlling rods are used to slow down the neutrons.
3. moderator is used to slow down the neutrons.
4. coolant is used to slow down the neutrons.

Fusion processes like combining two deuterium nuclei to form a He nucleus are impossible at ordinary temperatures and pressures. The reason is:

(i) Nuclear forces are short range.

(ii) Original nuclei must first break before combining with other nuclei.

(iii) Nuclei is negatively charged.

(iv) Nuclei is positively charged.

1. only (i)
2. (i) and (ii)
3. (ii) and (iv)
4. (i) and (iv)

In the nuclear decay given below :

_ZX^A ⟶ _Z+1Y^A ⟶ _Z-1B^A-4 ⟶ _Z-1B^A-4

The particles emitted in the sequence are :

1. α, β, γ
2. β, α, γ
3. γ, β, α
4. β, γ, α