Answer:
Option B
Explanation:
In series combination equivalent resistance
$R=R_{1}+R_{2}$
=6+4=$10k \Omega$
Error in combinbation
$\triangle R = \triangle R_{1}+\triangle R_{2}$
$=\frac{10}{100} \times 6+ \frac{10}{100} \times 4$
=$0.6+0.4=1$
$\frac{\triangle R}{R}=\frac{1}{10}=10$%