1. Jo's collection contains US, Indian and British stamps. If the ratio of US to Indian stamps is 5 to 2 and the ratio of Indian to British stamps is 5 to 1, what is the ratio of US to British stamps?

　　A. 5 : 1

　　B. 10 : 5

　　C. 15 : 2

　　D. 20 : 2

　　E. 25 : 2

　　2. A 3 by 4 rectangle is inscribed in circle. What is the circumference of the circle?

　　A. 2.5π

　　B. 3π

　　C. 5π

　　D. 4π

　　E. 10π

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