For the nuclear reaction:

${}_{92}U_{235}$ $+$ ${}_{0}n_1$ $\to$ ${}_{56}B{a}^{144}$ $$ $+$ $...$ $$ $+$ $3_0{n}^1$

The blank space can be filled by:

1. ${}_{26}K{r}^{89}$

2.  ${}_{36}K{r}^{89}$

3. ${}_{26}S{r}^{90}$

4.  ${}_{38}S{r}^{89}$

Fusion reaction takes place at a higher temperature because:

Which of the following is used as a moderator in nuclear reactors? 

1. Plutonium 

2. Cadmium 

3. Heavy water

4. Uranium 

If in nuclear reactor using U²³⁵ as fuel, the power output is 4.8 MW, the number of fissions per second is:
(Energy released per fission of U²³⁵ = 200 MeV watts, 1 eV = 1.6 X 10^–19 J)

1. 1.5×10¹⁷           

2. 3×10¹⁹           

3. 1.5×10²⁵           

4. 3×10²⁵