The moment of inertia of CO molecule is

I = $$\mu$$r² ....... (i)

where, $$\mu$$ = reduced mass of the CO molecule, r = distance between C and O or bond length

The reduced mass $$\mu$$ of the CO molecule is

$$\mu = {{{m_1}{m_2}} \over {{m_1} + {m_2}}} = \left[ {{{(12)(16)} \over {12 + 16}}} \right] \times {5 \over 3} \times {10^{ - 27}}$$ kg

But $$I = 1.87 \times {10^{ - 46}}$$ kg m² (From the above question)

From equation (i), we get

$${r^2} = {I \over \mu }$$

Substituting the values of I and $$\mu$$ in above equation, we get

$${r^2} = {{1.87 \times {{10}^{ - 46}}} \over {\left[ {{{12 \times 16} \over {28}} \times {5 \over 3} \times {{10}^{ - 27}}} \right]}}$$

or $${r^2} = {{1.87 \times {{10}^{ - 46}} \times 28 \times 3} \over {12 \times 16 \times 5 \times {{10}^{ - 27}}}}$$ or $$r = 1.3 \times {10^{ - 10}}$$ m