Explanation

(b)
Bond angle depends on the structure of molecule. If two molecules have same structure, then bond angle is decided by the electronegativity of central atom. Electrongeativity of central atom $\propto$ bond angle.
The bond angle of $H_{2}S$ is less than $H_{2}O$ because S is less electronegative than $H_{2}O$.
Hence, ${\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ H}_{2}O > H_{2}S$
$(104.5{^\circ})\ \ \ (92.2{^\circ})$
Further the $BeCl_{2}$ has linear structure, hence its bond angle is $180{^\circ}$. The $N_{2}O$ molecule also has linear structure with bond angle $180{^\circ}.$
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