The use of word at (A) is incorrect as 'could' is a modal verb so a main verb is required after it but 'typewriters' is a noun. Whereas word at (B) is contextually incorrect as typewriter being a machine cannot think. So, word at (A) and word at (B) will be swapped.
The correct sentence after rearrangement- He thinks typewriters could end up being replaced by processors or calculators or something.
Hence, option (b) is correct.
NOTE/-
Modal verb: A verb used with another verb to express an idea such as possibility that is not expressed by the main verb. The modal verbs in English are "can," "could," "may," "might," "must," "ought," "shall," "should," "will," and "would." They do not change their form (spelling) and they have no infinitive or participle (past/present). Example: I can speak Spanish. Here 'can' expresses the ability of the person to speak (main verb) Spanish. This ability cannot be expressed by the main verb 'speak'.
Study Notes
Category
