A number of students from Fibonacci Middle School are taking part in a community service project. The ratio of $8^{\text {th }}$-graders to $6^{\text {th }}$-graders is $7: 6$, and the the ratio of $8^{\text {th }}$-graders to $7^{\text {th }}$ graders is $4: 7$. What is the smallest number of students that could be participating in the project? (2013 AMC 8, Question 16) 
选项为:A:$$21$$  B:$$47$$  C:$$56$$  D:$$94$$  E:$$100$$  请回答其中一个选项.