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Given Expression, $latex \tan 4^{\circ}\cdot \tan 43^{\circ}\cdot \tan 47^{\circ}\cdot \tan 86^{\circ}$
$latex = \tan 4^{\circ}\cdot \tan 43^{\circ}\cdot \tan (90^{\circ}-43^{\circ})\cdot \tan (90^{\circ}-4^{\circ})$
$latex = \tan 4^{\circ}\times \tan 43^{\circ}\times \cot 43^{\circ}\times \cot 4^{\circ} = 1$
$latex \left [\because \tan \left ( 90^{\circ} – \theta \right ) = \cot \theta; \tan \theta\cdot \cot \theta = 1 \right ]$
Hence option [A] is correct answer.