18. A plane intersects a right circular cylinder of radius 1 to form an ellipse. If the major axis is 50% longer than the minor axis, the length of the major axis is
(A) 1 ; (B) $\frac{3}{2}$;
(C) 2 ;
(D) $\frac{9}{4}$;
(E) 3 .
18
E
18. The minor axis of the ellipse is parallel to the diameter of the circular base of the cylinder, so the length of the minor axis is 2. At this time, the length of the major axis is
$$
2+0.5 \times 2=3
$$