If the term independent of \( x \) in the expansion of \( \left(\sqrt{a}\,x^2+\frac{1}{2x^3}\right)^{10} \) is \( 105 \), then \( a^2 \) is equal to:
\( 9 \)
\( 2 \)
\( 4 \)
\( 6 \)