Quizzes: Subject Verb Agreement 3

For the following questions, determine whether the verb should be singular (ending in -s) or plural (not ending in -s) in order to agree with its subject.

The number of natural materials being replaced by synthetics (is/are) growing because unlike wood, leather, and ceramics, plastic is enormously versatile and
inexpensive to produce.
Located on the rim of Olduvai gorge (is/are) an excavation site and a museum that presents exhibitions pertaining to the gorge's history.
Whether the first birds evolved from arboreal or terrestrial ancestors (is/are) a source of lively debate among paleontologists.
Each of the illuminated manuscripts in the library's collection (was/were) unique, although most contained similar groups of texts accompanied by vividly colored decorations.
The first party of explorers to reach the South Pole (was/were) led by the Norwegian explorer Roald Amundsen, whose party arrived shortly ahead of a British team led by Robert Falcon Scott.
That Jane Goodall became the world's foremost expert on chimpanzees (was/were) hardly a surprise to those who observed her childhood fascination with animals.
A natural thief and spy, the jay, along with the crow and the raven, (belongs/belong) to a highly intelligent group of birds called the corvids.
The number of American students choosing to study abroad in countries in which English is not the primary language (has/have) been growing slowly but steadily over the past several decades.
Having an excessive amount of confidence in one's personal beliefs frequently (leads/lead) to poor decision-making, especially in organizational or political contexts.
Currents crisscrossing the deep waters of the ocean continuously (delivers/deliver) fresh oxygen, providing energy for armies of worms, fish, and other creatures that display
voracious appetites.