This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

[EX Q]: Passage: Modern electrification systems take AC energy from a power grid which is delivered to a locomotive and converted to a DC voltage to be used by traction motors. These motors may either be DC motors which directly use the DC or they may be 3-phase AC motors which require further conversion of the DC to 3-phase AC (using power electronics). Thus both systems are faced with the same task: converting and transporting high-voltage AC from the power grid to low-voltage DC in the locomotive. Where should this conversion take place and at what voltage and current (AC or DC) should the power flow to the locomotive? And how does all this relate to energy-efficiency? Both the transmission and conversion of electric energy involve losses: ohmic losses in wires and power electronics, magnetic field losses in transformers and smoothing reactors (inductors). Power conversion for a DC system takes place mainly in a railway substation where large, heavy, and more efficient hardware can be used as compared to an AC system where conversion takes place aboard the locomotive where space is limited and losses are significantly higher. Also, the energy used to blow air to cool transformers, power electronics (including rectifiers), and other conversion hardware must be accounted for. Question: What nowdays electrification systems can use?
[EX A]: DC motors which directly use the DC or they may be 3-phase AC motors

[EX Q]: Passage: Internal courtyards became more rare, except beside the stables, and the functional parts of the building were placed at the sides, or in separate buildings nearby hidden by trees. The views to and from the front and rear of the main block were concentrated on, with the side approaches usually much less important. The roof was typically invisible from the ground, though domes were sometimes visible in grander buildings. The roofline was generally clear of ornament except for a balustrade or the top of a pediment. Columns or pilasters, often topped by a pediment, were popular for ornament inside and out, and other ornament was generally geometrical or plant-based, rather than using the human figure. Question: What often topped pilasters of columns?
[EX A]: pediment

[EX Q]: Passage: The standard SNES controller adds two additional face buttons (X and Y) to the design of the NES iteration, arranging the four in a diamond shape, and introduces two shoulder buttons. It also features an ergonomic design by Lance Barr, later used for the NES-102 model controllers, also designed by Barr. The Japanese and PAL region versions incorporate the colors of the four action buttons into system's logo. The North American version's buttons are colored to match the redesigned console; the X and Y buttons are lavender with concave faces, and the A and B buttons are purple with convex faces. Several later consoles derive elements of their controller design from the SNES, including the PlayStation, Dreamcast, Xbox, and Wii Classic Controller. Question: How many shoulder buttons do SNES controllers have?
[EX A]:
two