Sentence Structure at the 700-800 Level

Hard-tier sentence structure items make every answer choice grammatical in isolation — the error exists only in how the pieces connect. Four archetypes cover nearly everything:

• Dangling openers — a long participial phrase, then the whole main clause as the blank. The first noun after the comma must be the thing the phrase describes. The traps wear four costumes: an abstract noun (the conclusion, preservation), the placeholder it, a possessive (Bergstrom's maps — the possessor doesn't count), and a related-but-wrong noun.
• Agreement across the gap — the nearest noun to the verb always has the wrong number. Anchors: collection / variety / number of / each / neither stay singular; inverted sentences put the subject after the verb; neither...nor agrees with the nearer subject; along with / together with never pluralizes.
• Tense logic — by the time + past event → past perfect; since + past date / ever since → present perfect; a closed past window → simple past. Wrong options are real tenses on the wrong timeline.
• Parallelism under correlatives — not only...but also, not...but, less...than: copy the exact form after the first half and demand it after the second.

Speed comes from mechanical moves: strike the interveners, un-invert the inversion, match the correlative character for character.