telling you you're standing straight. That can be annoying-that's why some people feel sick."可知宇航员在大脑接收到矛盾的信息时会感到恶心。故选D项。

4.细节理解题。根据最后一段倒数第一、二句"The focus on fitness is as much about science and the future as is about keeping any individual astronaut healthy...NASA is worried about two things :... and, more importantly, how maintain strength and fitness..."可知美国国家宇航局对宇航员主要的担心之一是如何在太空长久地保持健康。故选B项。

　　Planning a visit to the UK? Here we help with ways to cut your costs.

STAY AWAY FROM THE STATION If traveling to your destination by train,you may want to find a good base close to the station,but you could end up paying more for the sake of convenience at the start of your holiday.

Don't be too choosy about the part of town you stay in.Booking two months in advance,the cheapest room at Travelodge's Central Euston hotel in London for Saturday 22 September was ￡95.95.A room just a tube journey away at its Covent Garden hotel was￡75.75.And at Farringdon,a double room cost just ￡62.95.

LOOK AFTER YOURSELF Really central hotels in cities such as London,Edinburgh and Cardiff can cost a fortune,especially at weekends and during big events.As an alternative consider checking into a self-catering flat with its own kitchen.Often these flats are hidden away on the top floors of city centre buildings.A great example is the historic O'Neill Flat on Edinburgh's Royal Mile,available for￡420 for five days in late September,with room for four adults.