Question

convert simple sentence into complex sentence i did not think fit to reply to his writings

Answer 1

I did not think fit to reply to what he wrote....

Answer 2

A complex sentence consists of one main clause and one or more subordinate clauses joined together with the help of subordinating conjunction(s).

Two clauses connected by relative pronouns or relative adverbs are also examples of complex sentences.

Writing a complex sentence is easy if you have a basic understanding of conjunctions and relative pronouns.