如图是缩手反射示意图，下列说法错误的是（　　）

下列现象，你认为哪一项是可以发生的（    ）

根据结构对有机物进行分类，有助于对其性质的掌握．

①有机物苯属于　 ____　（填字母）． a．芳香烃  b．烯烃        c．炔烃

②下列有机物属于酚类的是　 ____　（填字母）．

③纤维素属于 ____　 （填字母）．a．糖类      b．油脂     c．蛋白质．

已知函数$f\left(x\right)$是定义在R上的单调增函数且为奇函数，数列$\left\{a_n\right\}$是等差数列，$a_{1007}>0$，则$f\left(a_1\right)+f\left(a_2\right)+f\left(a_3\right)+\cdots +f\left(a_{2012}\right)+f\left(a_{2013}\right)$的值（    ）．

Walk For Charity

Dear Friend,

    Please join us for our annual Walk For Charity.Starting in Weldown,you and your friends can choose a delightful 10,20 or 30 kilometers' route.

    The money raised will provide support to help people all over the world.Start collecting your sponsors now and then simply come along on the day.Please read the instructions below carefully,especially if you require transport to and from Weldown.

    See you on Sunday 15 April.

    V Jessop: Walk coordinator

    PS.Well done to last year's walkers for helping to raise a grand total of ￡21,000.The money has already been used to build a children's playground.

    START TIME:

    30 km: 8-10 am      20 km: 8-10:30 am      10 km: 8-11:30 am

    The organizers reserve the right to refuse late-comers.

    CLOTHING should be suitable for the weather.If rain is forecast,bring some protection and be prepared for all possibilities.It is better to wear shoes that have been worn in,rather than ones that are new.

    ROUTE MAPS will be available from the registration point.The route will be sign-posted and arranged.Where the route runs along the road,walkers should keep to one side in single file,facing oncoming traffic at all times.If you need help along the route,please inform one of the staff.

    Free car parking is available in car parks and on streets in Weldown.

    BUSES:

    For the 10 and 20 kilometers' routes,a bus will be waiting at Fenton to take walkers back to Weldown.The bus will leave every half hour starting at midday.The service is free and there is no need to book.