Q54. Total number of optically active compounds from the following is $\_\_\_\_$\\
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$$\mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { OH } \text {, }$$
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$\mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { Cl }$,\\
$\left( \mathrm { CH } _ { 3 } \right) _ { 2 } \mathrm { CH } - \mathrm { CH } _ { 2 } - \mathrm { CH } _ { 2 } - \mathrm { Cl }$