'there is a sufficiently number' vs 'there are a sufficient number'

[Schwartz]

When______of similar research projects, similar discoveries tend to occur simultaneously.
a) there is a sufficiently number b) there are a sufficient number
correct answer is b) but I don't understand why they use 'there are' with 'a' it should be used with plural, isn't it?
and i don't know why they use sufficient instead of sufficiently.

[Milanya]

The Number Of versus A Number Of

A number of should be used with a plural verb. Think of it this way: A number of equates to the word they.
 A number of fans buy tickets at the game. (They buy tickets.)
 A number of dogs in our neighborhood actually like the mailman. (They like the mailmam.)
On the other hand, when using the number of, use a singular verb. The number of equates to the word it.
 The number of snowstorms this year was more than expected. (It was more than expected.)
 The number of dogs in our neighborhood has grown over the past several years. (It has grown.)
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con·text - The part of a text or statement that surrounds a particular word or passage and determines its meaning.

[Schwartz]

thank you.
and what about 'sufficiently' and 'sufficient'?

[Esl_Expert]

Hello Schwartz,

The word "sufficient" in an adjective, and the word "sufficiently" is an adverb.
An adverb is used to modify (1) a verb, or a it can modify (2) another adverb or (3) an adjective:

1. I drive carefully.
2. I drive extremely carefully.
3. I am an extremely careful driver. (The word "extremely" modifies the adjective "careful".)

An adjective describes a noun:

- I am a careful driver.

You need an adjective ("sufficient") in your sentence because the word it modifies is a noun ("number").

Are you by any chance German, Schwartz?

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“A man's character may be learned from the adjectives which he habitually uses in conversation.” ~ Mark Twain

[Darkangel12891]

However, there is a sentence " she smoke very heavily"
heavy is an adj, heavily is adv.
Thus how can it be used here?

[Esl_Expert]

Hello Darkangel,

Your sentence should be written this way (in the simple present tense):

- She smokes very heavily.

The word "heavily is an adverb and it modifies the verb in the sentence ("smokes").
The word "very" is also an adverb, and it modifies "heavily" in the sentence.

This is the same sort of sentence as the second example in my previous post:

[Schwartz]

I thought I could use a) there is a sufficiently number, "sufficiently" to modify verb to be "is" in the sentence.

[Milanya]

[Schwartz]

why can't I use "sufficiently (adv.)" to modify "is(verb)"?

[Esl_Expert]

Hello Schwartz,

The verb "be" is what we call a "linking verb". (There are also other verbs that are used as linking verbs.) A linking verb can link an adjective directly to the subject of a sentence.

Look at these sentences:

- Her dog is big.
- His dog is playful.
- Her dog is vicious.
- His dog is loyal.

The words big, playful, vicious and loyal are all adjectives, and they describe the subject (dog). These adjectives are linked directly to the subject of the sentence by the linking verb "be" (is).

Your sentence is a bit different. In your sentence, there is a very clear indication that the word "sufficient" modifies the noun, and that is the fact that the indefinite article was used before the word sufficient:

- a sufficient number

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“I cannot find language of sufficient energy to convey my sense of the sacredness of private integrity.” ~ Ralph Waldo Emerson