Which one is a conversion of a simple sentence into complex?

একটি Complex Sentence এ একটি principal clause এবং এক বা একাধিক subordinate clause থাকে।
অপশনগুলো বিশ্লেষণ:
১. 'To his colossal disgrace, he betrayed his country' - এটি Simple Sentence।
২. 'He must work very hard and walk up for the last time' - এটি Compound Sentence (and যুক্ত)।
৩. 'He confessed that he was guilty' - এটি Complex Sentence। এখানে 'He confessed' হলো principal clause এবং 'that he was guilty' হলো noun clause। এর Simple form হলো 'He confessed his guilt'।
৪. 'We must eat or we cannot live' - এটি Compound Sentence (or যুক্ত)।