26. B. than

The sentence compares the speed of doing things with and without computers, so "than" is the correct choice.
27. C. more rapidly

The sentence needs a comparative adverb to describe how computers do calculations compared to a mathematician. "More rapidly" is the correct choice.
28. D. If

The sentence introduces a conditional statement about what a computer can do "if" it is programmed properly.
29. A. work

The sentence describes what a computer can do when programmed correctly, so "work" is the most suitable verb.
30. B. scientific

The sentence refers to the "history of computer science," so "scientific" is the correct adjective.
31. C. between

The sentence compares the old and modern computers, so "between" is the correct preposition.
32. B. less

The sentence states that old computers work "less" efficiently than modern ones.
33. A. which

"Which" is a relative pronoun that refers back to "applied programs."
34. B. from

The sentence indicates that information is obtained "from" the internet.
35. A. are

The sentence is describing a general fact about computers, so the plural verb "are" is correct.