21. An optical microscope magnifies as much as 2,000 times, but an electron microscope_____ as much as a million times.
A. magnifying
B. it magnifies
C. can magnify
D. magnify it

Pada soal ini membutuhkan main verb utk klausa kanan. Main verb bisa dalam bentuk modals + bare infinitive.
Ambil opsi C.

22. If scientific estimates are accurate, _____ with the Earth about 20,000 years ago.
A. the Canon Diablo meteorite collided
B. the collision of the Canon Diablo meteorite
C. the Canon Diablo meteorite colliding
D. colliding the Canon Diablo meteorite

Pada soal ini membutuhkan subjek dan main verb untuk klausa kanan.
Ambil opsi A. subjek (the Canon Diablo meteorite) main verb (collided)

23. _____ of the Pueblo Indians centered on intensive agriculture.
A. The economic activity
B. Because the economic activity
C. The economy was active
D. When the economic activity

Pada soal ini satu klausa dan membutuhkan subjek. Main verb sudah ada (centered)
Ambil opsi A. The economic activity.

24. In popular terminology, any long snowstorm with_____ is called a blizzard.
A. the amount of wind is large
B. a large amount of wind
C. it is very windy
D. very windy

Pada soal ini membutuhkan struktur noun. Tahu darimana? dari preposition with.
A dan C salah karena ada main verb (is).
D salah karena bukan struktur noun (adjective windy)

25. Nuclear power can be produced by fusion, _____ produced by fission.
A. it can also be
B. it can also
C. and it can also be
D. and it can also

Pada soal ini 2 klausa dan butuh conjunction serta main verb paralel dengan klausa kiri.
Ambil opsi C. conjunction (and), subjek (it), main verb dalam modals pasif (can + also + be + V3)

26. _____, igneous rocks may be changed into gneisses.
A. The temperature is high
B. If the temperature is high
C. High temperatures
D. If high temperature

Pada soal ini 2 klausa butuh conjunction serta subjek dan main verb untuk klausa kiri.
Ambil opsi B. conjunction (if), subjek (the temperature), main verb (is high).

27. In 1905, Henry Flagler_____ his plans to extend his Florida East Coast Railway out across the sea to Key West
A. it was announced
B. announcement
C. the announcement of
D. announced

Pada soal ini ambil opsi main verb past polos.
Ambil opsi D.

28. The sound_____ from a vibrating object will be high or low depending on the number of vibrations.
A. comes
B. it is coming
C. is coming
D. coming

Pada soal ini subjek sudah ada (The sound), main verb sudah ada (will be).
Jadi ambil extra verb aktif pada opsi D. coming.

29. During the late 1880s, urban streetcars were electrified through _____large motors.
A. they used
B. used
C. the use of
D. when they used

Pada soal ini di depan gap ada through, maka artinya kita butuh noun atau struktur word order (artikel + noun + of + noun)
ambil opsi C. artikel (the), noun (use), preposisi (of)

30. ____almost 274 square miles, but 96 percent of the park is under water.
A. Although Biscayne National Park encompasses
B. Biscayne National Park encompasses
C. Biscayne National Park encompassing
D. Biscayne National Park

Soal ini punya 2 klausa dan kita butuh subjek serta main verb untuk klausa kiri.
Ambil opsi B. Subjek (Biscayne National Park), main verb (encompasses) = mencakup