<image>I surrounded the wooden circle (see picture) using $a \mathrm{~cm}$ of thread. After that I surrounded by thread the wooden square –– $b \mathrm{~cm}$ of thread was enough for that. How much thread (in $\mathrm{cm}$ ) would be enough to surround the three wooden circles without moving them?
A. 3a
B. 2a+b
C. a+2b
D. 3b
E. a+b