A4. If we halve the straight angle, divide the half into thirds, the third into fifths, and the fifth into sixths, the sixth of the fifth of the third of the half of the straight angle measures:
(A) $1^{\circ}$
(B) $2^{\circ}$
(C) $30^{\circ}$
(D) $1^{\prime}$
(E) $30^{\prime}$
A4. Half of the drawn angle is $90^{\circ}$, a third of this is $30^{\circ}$, a fifth of the obtained is $6^{\circ}$ and a sixth of the latter is $1^{\circ}$.