He spoke _________ he had been mad.

• as if/as though (conjunction)
- as if/as though এর পূর্বে present indefinite tense থাকলে as if/as though এর পরে past indefinite হয়।
- be verb থাকলে সবসময় were হয়।
Example: He speaks as if he were mad.

• as if/as though এর পূর্বে Past indefinite tense থাকলে as if/as though এর পরে past perfect হয়।
Example: He spoke as though he had been mad.

"We use as if and as though to make comparisons. They have a similar meaning. We use as if and as though to talk about an imaginary situation or a situation that may not be true but that is likely or possible. As if is more common than as though."
- Cambridge Dictionary

অন্যদিকে,
- if (যদি),
- then (তখন),

Source:
1. Cambridge Dictionary.
2. Accessible Dictionary by Bangla Academy.