You must give a signal either by hand and arm or by a signal device:
a) only if other traffic is affected by your movement
b) only if you are driving a truck or car
c) only at night
d) anytime you change lanes

D) Anytime you change lanes

Explanation:

Correct way to execute a change of direction maneuver :

1 - The driver must warn by means of optical signals any maneuver that implies a lateral or backward displacement of his vehicle, as well as his intention to immobilize it or to slow down his gear in a considerable way. Such optical warnings will be made well in advance of the start of the maneuver, and, if they are bright, they will remain in operation until the end of the maneuver.

2 - Unless the road is conditioned or signposted to perform it in another way, it will be as close as possible to the right edge of the road, if the change of direction is to the right, and to the left edge, if it is to the left and the road is One way. If it is on the left, but the road through which it circulates is two-way traffic, it will adhere to the longitudinal mark of separation between the senses or, if it does not exist, to the axis of the road, without invading the area destined to the Wrong Way; when the road is two-way traffic and 3 lanes, separated by dashed longitudinal lines, should be placed in the center. In any case, the placement of the vehicle in the appropriate place will be carried out with the necessary advance and the maneuver in the least possible space and time.

3 - If the change of direction is on the left, it will leave the center of the intersection on the left, unless it is conditioned or marked to leave it on the right .