The associative law for vector addition is

• a$(\vec{u}+\vec{v})+\vec{w}=\vec{u}+(\vec{v}+\vec{w})$
• b$\vec{u}+\vec{v}=\vec{v}+\vec{u}$
• c$\vec{u}+\vec{0}=\vec{u}$
• d$\vec{u}+(-\vec{u})=\vec{0}$