已知$\sin (\frac{\mathrm{\pi }}{3}-x)=\frac{3}{5}$，则  $\cos (\frac{5\mathrm{\pi }}{6}-x)=$ （    ）

    Tom and Mike had a very good time last Sunday.That morning，they1at six o'clock and dressed(穿衣)themselves.2having breakfast，they went to the park.It's in the centre of the city. In the park.there were a lot of nice flowers.Mike wanted to 3one，but Tom stopped(阻止)him.He told Mike it was not.4to pick flowers.Then they went to the lake.By the lake,they saw a small5.They jumped into it and started a tour on the lake.Two hours6,they left the lake and walked up the hill(小山)near the lake.They got to the top at half past eleven.There they had their lunch.7did they have for lunch?Eggs，bread and oranges.In the afternoon,they 8home.When their mother asked them about the morning，9answered，"It was great.We10ourselves(我们自己)all the morning."

根据入射光线和折射光线，在图中的虚线框内画出适当的类型的透镜．

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（2015•烟台）如图，将一个圆柱体放置在长方体上，其中圆柱体的底面直径与长方体的宽相平，则该几何体的左视图是（　　）