Identify the correct sentence:
The room was darkened by switching off all the lights.
The room was darkened switching off all the lights.
The room was darkened to switch off all the lights.
Switching off all the lights the room was darkened.
সঠিক উত্তর:
The room was darkened by switching off all the lights.
ব্যাখ্যা ও নোট:
এখানে 'by + gerund' ব্যবহার করে কোনো পদ্ধতি বা কারণ প্রকাশ করা হয়েছে।