The radiation that ________ during the decay of radioactive atomic nuclei is known as gamma radiation.

Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!

Sentence Structure

• The radiation
• that (?) during the decay of radioactive atomic nuclei
• is known as gamma radiation.

Understanding the Meaning

Let's start reading from the beginning:

'The radiation...'

• We're talking about a specific type of radiation.

'that ______ during the decay of radioactive atomic nuclei'

• This is where we have the blank.
• Let's look at the choices:
  • occurs (singular)
  • have occurred (plural)
  • occur (plural)
  • are occurring (plural)
• So we're deciding between singular and plural verb forms.

To see what works here, let's understand the complete sentence!

• The word 'that' here is referring back to 'radiation' - it's introducing a describing clause that tells us more about this radiation.
• 'during the decay of radioactive atomic nuclei' - This tells us WHEN this radiation does its thing - it happens during the decay process of radioactive atoms.
• 'is known as gamma radiation' - This is telling us what this particular radiation is called.

So the complete picture is:

• The sentence is describing radiation that occurs during radioactive decay, and telling us this radiation is called gamma radiation.

What do we notice about the structure here?

• The word 'that' is the subject of the verb in the blank.
• 'That' refers back to 'radiation' - which is singular.
• When a describing word like 'that' refers to something, the verb needs to match whether that something is singular or plural.
• 'Radiation' is singular, so we need a singular verb.

Looking at our choices:

• Only 'occurs' is singular.
• The others (have occurred, occur, are occurring) are all plural forms.

Also, since we're stating a general scientific fact about radiation, we need simple present tense, not a form suggesting ongoing action right now or completed action.

So we need: occurs

GRAMMAR CONCEPT APPLIED

Matching Verbs to Subjects in Describing Clauses

When you have a describing clause that starts with 'that' or 'which,' the verb in that clause needs to agree with the noun being described:

Pattern:

• Singular noun + that/which + singular verb
• Plural noun + that/which + plural verb

Examples:

• The student that studies hard will succeed
  • 'student' is singular → 'studies' is singular
• The students that study hard will succeed
  • 'students' is plural → 'study' is plural

In our sentence:

• The radiation (singular) that occurs (singular) during decay...
  • 'radiation' is singular, so we need the singular verb 'occurs'

Technical note: The words 'that' and 'which' are called relative pronouns in grammar terms. When they act as the subject of their clause, the verb must agree with their antecedent (the noun they refer back to).