81. Part of the electricity used in the United States today come from hydroelectric sources.

electricity uncountable, ubah come jadi comes.

82. The languages of the world presents a vast array of structural similarities and differences.

languages plural, ubah presents jadi present.

83. The rise of multinationals have resulted in a great deal of legal ambiguity because multinationals can operate in so many jurisdictions.

rise tunggal, ubah have jadi has

84. All of the east-west interstate highways in the United States has even numbers, while north-south interstate highways are odd-numbered.

highways plural, ubah has jadi have

85. When a massive star in the large Magellanic Cloud exploded in 1987, a wave of neutrinos were detected on Earth.

a wave tunggal, ubah were jadi was

86. Some of the agricultural practices used today is responsible for fostering desertification.

practices jamak, ubah is jadi are

87. Every open space in the targeted area that has grass and a few bushes are occupied by the white-crowned sparrow.

every tunggal, ubah are jadi is

88. Krakatoa is remembered as the volcano that put so much ash into the air that sunsets around the world was affected for two years afterward.

sunsets plural, ubah was jadi were

89. ________ the earliest system of writing.
A. The constitution of pictograms
B. Pictograms in the constitution
C. Constitute the pictograms
D. Pictograms constitute

butuh subjek dan main verb, ambil opsi D.

90. At temperatures________ absolute zero, substances possess minimal energy.
A. approach
B. approaches
C. approaching
D. they approach

butuh extra verb, ambil present participle pada opsi C.