He runs fast as though he ______ a mad.

- As if/ as though যুক্ত sentence যদি unreal/ অপ্রকৃত/কাল্পনিক বুঝায় তাহলে As if/ as though এর পর were বসে।
- তাই সঠিক উত্তর: He runs fast as though he were a mad.

অন্যদিকে,
• As if/ as though ‘যেন’ অর্থ প্রকাশ করে Sentence এর প্রথম অংশে present indefinite হলে পরের অংশে past indefinite হয়।
- He tells the matter as if he knew it.

• As if/ as though যুক্ত sentence এর প্রথম অংশে past tense হলে পরের অংশে past perfect হয়।
- He told the matter as if he had known it.

Source: Advanced Learner’s Grammar and Composition by Chowdhury and Hossain.