English Grammar Basics | Time Prepositions, Modal Verbs, and Comparisons

Use "at" before the clock time 9:00, "on" before the day Monday, and "in" before the month September. The complete sequence is therefore "at 9:00 on Monday in September." Time prepositions vary according to whether the expression is a clock time, day, or month.

The phrase "five years" is a duration, so the first phrase is "for five years." The year 2021 identifies the starting point of the continuing situation, so the second phrase is "since 2021." Both words can accompany continuing situations, but "for" measures duration and "since" marks the start.

The words after the blank form the clause "the repairs were finished," with a subject and a verb. When the endpoint in a from-to relationship is expressed as a clause, use "until." "To" can precede a noun phrase in a sequence such as "from Monday to Friday," but not the clause in this sentence.

The speaker is recommending a helpful action, not stating a rule or prohibition, so "should" is appropriate. "Mustn't" and "can't" would prohibit the action, while "don't have to" would say that it is unnecessary, reversing the intended advice.

Because photography is prohibited, the first phrase is "mustn't take photos." Because the audio guide is optional, "don't have to rent" means that visitors may rent one but are not required to. "Mustn't" means an action is not allowed; "don't have to" means there is no obligation.

The polite pattern for asking another person to act is "Could you" followed by the base form of the verb. "May I" can ask permission for the speaker to act, but "May you" is not the standard request pattern here. "Shall you" and "Must you" do not express the intended polite request either.

Because the two desks have equal widths, use "as wide as" to express the same degree of width. "Wider than" would say that Desk A is wider, contradicting the measurements. "The widest" identifies the highest degree within a group rather than equality between two items.

The sentence compares two versions and names the second after "than," so the comparative phrase "easier to follow than" is appropriate. Because "easy" ends in a consonant plus y, its comparative changes the y to i before adding -er. "More easier" incorrectly marks the comparative twice, while "the easiest" is a superlative.

Route A's travel time is the lowest within a group of three, so the superlative "the shortest" is required. "Shorter" is a comparative form used to say that one of two items has less length or duration. Here, "of the three" defines a group and calls for the superlative, normally with "the."

Linked changes are expressed with "the" plus a comparative in each clause, making "The stronger ..., the more difficult ..." correct. "Strongest" and "most difficult" are superlatives and do not fit this construction for two changing degrees.