Answer:
C
Step-by-step explanation:
[tex]\frac{10}{a} =sin 60\\a=\frac{10}{sin~60}\\=\frac{10}{\frac{\sqrt{3} }{2} } \\=\frac{20}{\sqrt{3}} \times\frac{\sqrt{3}}{\sqrt{3}} \\=\frac{20 \sqrt{3}}{3}[/tex]
