WHO.
Errors connected with the use of this word are very common, even amongst good speakers.
"Who did you see?" "Who do you know?" and "Who did you hear?" are wrong: whom should be used, for it is the object of the transitive verbs, see, know and hear. Who in such sentences as: "Who are you looking at?" and "Who are you writing to?" should likewise be changed into whom, for it is the object of the prepositions at and to.
ADJECTIVES AND ADVERBS.
Adjectives are often erroneously used for adverbs in sentences like the following: "This is an uncommon good portrait," "It is a miserable poor painting. "Uncommonly good and miserably poor are right.
Adverbs are still more commonly used for adjectives. "Mary looked beautifully at the party," and "Janauschek looked majestically on the stage," are incorrect, for it is intended to describe the appearance of Mary and Janauschek, not their manner of looking; therefore the adjectives beautiful and majestic should be used.
When two objects are compared, the comparative degree should be used. "William is the heaviest of the two," and "Which is the most desirable—health or wealth?" ought to be, "William is the heavier of the two," and "Which is the more desirable—health or wealth?"
THESE, THOSE.
The plural demonstratives these and those are often erroneously used with singular nouns, as: "I don't like these kind of people," and "Those sort of things are very embarrassing." Kind and sort are singular and should have this and that.