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.

[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?
[A]: DC motors which directly use the DC or they may be 3-phase AC motors


[Q]: Passage: Cultural depictions of dogs in art extend back thousands of years to when dogs were portrayed on the walls of caves. Representations of dogs became more elaborate as individual breeds evolved and the relationships between human and canine developed. Hunting scenes were popular in the Middle Ages and the Renaissance. Dogs were depicted to symbolize guidance, protection, loyalty, fidelity, faithfulness, watchfulness, and love. Question: Thousands of years ago, dogs were depicted on the walls of what?
[A]: caves.


[Q]: Passage: Notable athletes include swimmer Sharron Davies, diver Tom Daley, dancer Wayne Sleep, and footballer Trevor Francis. Other past residents include composer journalist and newspaper editor William Henry Wills, Ron Goodwin, and journalist Angela Rippon and comedian Dawn French. Canadian politician and legal scholar Chris Axworthy hails from Plymouth. America based actor Donald Moffat, whose roles include American Vice President Lyndon B. Johnson in the film The Right Stuff, and fictional President Bennett in Clear and Present Danger, was born in Plymouth. Question: What is Dawn French's job?
[A]:
comedian