Champion Swim Club ____(found) in 2006 by former World Cup Swimming Champion Ms. Vivian Wang and is the first competitive organization for expats' children and adults in Shanghai. The club ____(provide) a structured program focused on the long-term development of its swimmers. Members will be assessed and given the opportunity____(train) with swimmers of a similar standard and level under the supervision of ____(lead) internationally experienced swimming coaches.

    So far, we____(create) a program that caters to swimmers of all ages and abilities. In addition to ensuring proper technique and conditioning, Swimmers____(place) in groups by the coaching staff after a stroke technique assessment session. The program has been designed by a world class coaching team that focuses on all of the elements and techniques that will result students maximizing their potential to enjoy and____(compete) at a competitive level.

    The coaching team comprises former World Cup Swimming Champion Vivian Wang as Head Coach and a number of highly experienced professional coaches will work together____(provide) a developmental swimming program where there is avenue for advancement through to higher levels. The leader of the club said, “I think we____(do) some useful things. If everyone spread the spirit, there ____(be) more champions in China. ”

$△$ABC是边长为2的等边三角形，已知向量$\overrightarrow{a}$,$\overrightarrow{b}$满足$\overrightarrow{AB}=2\overrightarrow{a},\overrightarrow{AC}=2\overrightarrow{a}+\overrightarrow{b}$,则下列结论中正确的是____。（写出所有正确结论得序号）.
①$\overrightarrow{a}$为单位向量；②$\overrightarrow{b}$为单位向量；③$\overrightarrow{a}$⊥$\overrightarrow{b}$；④$\overrightarrow{b}$//$\overrightarrow{BC}$ ;⑤ （4$\overrightarrow{a}$+$\overrightarrow{b}$）⊥$\overrightarrow{BC}$。

旅客坐在火车或汽车上时，即使闭上眼睛，也能够准确辨别行驶速度的变化和是否在上下坡，接受这种刺激的感受器位于____ .