A current of 2 A flows through a $2 \Omega$ resistor when connected across a battery. The same battery supplies a current of 0.5 A when connect across a $ 9 \Omega$ resistor. The internal resistance of the battery is :

Question

( A ) $ 1 \Omega$
( B ) $1/3 \Omega$
( C ) $0.5 \Omega$
( D ) $1/4 \Omega$