Step 1: Use the change in efficiency:
The efficiency rises by $0.3$ when $T_2$ falls by 45 K: $\Delta\eta=\dfrac{\Delta T_2}{T_1}$, so $\dfrac{45}{T_1}=0.3$ and $T_1=150$ K.
Step 2: Find T2:
$\eta=0.2$ gives $T_2=T_1(1-0.2)=120$ K.
Step 3: Pick:
$T_1=150$ K, $T_2=120$ K. Option A.
Final Answer:
Lowering T2 by 45 K raises efficiency by 0.3, so T1 = 150 K and T2 = 120 K.
\[ \boxed{\text{(A) }150\ \text{K},\ 120\ \text{K}} \]