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: In 1986, the Compact of Free Association with the United States entered into force, granting the Republic of the Marshall Islands (RMI) its sovereignty. The Compact provided for aid and U.S. defense of the islands in exchange for continued U.S. military use of the missile testing range at Kwajalein Atoll. The independence procedure was formally completed under international law in 1990, when the UN officially ended the Trusteeship status pursuant to Security Council Resolution 683. Question: What document granted sovereignty to the Marshall Islands?
[EX A]: the Compact of Free Association

[EX Q]: Passage: Between 64 and 104 major aftershocks, ranging in magnitude from 4.0 to 6.1, were recorded within 72 hours of the main quake. According to Chinese official counts, "by 12:00 CST, November 6, 2008 there had been 42,719 total aftershocks, of which 246 ranged from 4.0 MS to 4.9 MS, 34 from 5.0 MS to 5.9 MS, and 8 from 6.0 Ms to 6.4 MS; the strongest aftershock measured 6.4 MS." The latest aftershock exceeding M6 occurred on August 5, 2008. Question: How many shocks ranged from 4.0 MS to 4.9 MS?
[EX A]:
246