一名运动员在百米赛跑中，测得他在7s末的速度为9m/s，10s末到达终点的速度为10.2m/s，则他在全程内的平均速度是（   ）

甲、乙两种商品原来的单价和为100元，因市场变化，甲商品降价10%，乙商品提价40%，调价后两种商品的单价和比原来的单价和提高了20%、若设甲、乙两种商品原来的单价分别为x元、y元，则下列方程组正确的是（  ）

    Personal planes which can take off noiselessly from the back garden will be possible within two years.

    Lilium Aviation is inventing an electric two-seater airplane which  takes just 20 hours to learn to fly and can travel at speeds of  250mph.More importantly, the small plane, which weighs just 25kg, can take off vertically which means it does not need to fly from an airport, but could be parked outside a house or in a garden. The company says the design will “open the door to a new class of simpler, quieter and environmentally friendly planes” and will be possible from 2018.

    “Our goal is to develop an airplane for use in everyday life,” said Daniel, CEO and one of the company's four founders. "We are going for a plane that can take off and land vertically and does not need the difficult and expensive infrastructure of an airport.

    Although helicopters offer a choice, they are very noisy and difficult to fly and require expensive licenses. They also have no backup if the rotor fails, making them costly to build and keep. While firstly limited to airfields, the Lilium airplane will eventually take off vertically from almost anywhere – even from back gardens – it needs only an open flat area of 50 ft. by 50ft (15 m x 15m).

    The plane is classed as a Light Sport Aircraft for two users, with the pilot's license requiring 20 hours' minimum training – almost like taking a driving license. It is intended for fun flying during daylight, in good weather conditions and in least crowded airspace up to 3 km altitude. The airplane would have to follow the same flight laws as helicopters.

阅读下面的文言文，完成下列各题。

    徐谊，字子宜，一字宏父，平阳人。乾道八年进士，累官太常丞。孝宗临御久，事皆上决，执政惟奉旨而行，群下多恐惧顾望。谊谏曰：“若是则人主日圣，人臣日愚，陛下谁与共功名乎？”及论乐制，谊对曰：“宫乱则荒，其君骄；商乱则陂，其官坏。”上遽改容曰：“卿可谓不以官自惰矣。”

    知徽州，陛辞，属光宗初受禅，谊奏：“三代圣王，有至诚而无权术，至诚不息，则可以达天德矣。”至郡，歙县有妻杀夫系狱，以五岁女为证，谊疑曰：“妇人能一掌致人死乎？”缓之未覆也。会郡究实税于庭，死者父母及弟在焉，乃言：“我子欠租久系，饥而大叫，役者批之，堕水死矣。”然后冤者得释，吏皆坐罪，阖郡以为神。

    孝宗疾浸棘上久稽定省谊入谏退告宰相曰上慰纳从容然目瞪不瞬意思恍惚真疾也宜祷祠郊庙进皇子嘉王参决丞相留正不克用。

    孝宗崩，上不能丧。谊与少保吴琚议，请太皇太后临朝，扶嘉王代祭。及将禫，正忧惧，仆于殿庭而去。谊以书谯赵汝愚曰：“自古人臣为忠则忠，为奸则奸，忠奸杂而能济者，未之有也。”汝愚问策安出，谊曰：“此大事，非宪圣太后命不可。而知阁门事韩侂胄，宪圣之戚也，同里蔡必胜与侂胄同在阁门，可因必胜招之。”侂胄至，汝愚以内禅议遣侂胄请于宪圣，侂胄因内侍达汝愚意，宪圣许之。

    宁宗即位，侂胄恃功，以赏薄浸觖望。谊告汝愚曰：“异时必为国患，宜饱其欲而远之。”不听。

    汝愚雅器谊，除授建明多咨访，谊随事裨助，不避形迹，怨者始众。尝劝汝愚早退，汝愚亦自请。侂胄疑将排己，首谒谊，退束装，冀谊还谒，留之通殷勤，谊不往。

    初，金攻庐、楚不下，留兵缀濠州以待和，时时钞掠，淮人大惊。谊昼夜拊循，益严备御。朝廷惧生事，移知隆兴府以卒，后谥忠文。

（《宋史•列传一五六》）

【注释】觖：不满意。