The bacteria in milk are destroyed when it _______ heated to 80 degree Celsius.
is
Bacteria Destruction: Understanding Verb Tense
The question asks us to choose the correct verb form to complete the sentence: "The bacteria in milk are destroyed when it _______ heated to 80 degree Celsius." This sentence describes a scientific fact or a general truth about what happens to bacteria in milk when it reaches a specific temperature.
Grammar of Scientific Facts: The Zero Conditional
In English grammar, when we talk about general truths, scientific facts, or habitual actions where a certain condition always leads to a certain result, we use a structure often referred to as the Zero Conditional. The structure of the Zero Conditional is:
- If/When + simple present tense (condition), simple present tense (result).
In the given sentence:
- The result is: "The bacteria in milk are destroyed." This is in the simple present tense (passive voice).
- The condition is: "when it _______ heated to 80 degree Celsius." For consistency with a general truth, this clause also needs to be in the simple present tense.
Analyzing the Options for Milk Heating
Let's examine each option to determine the most appropriate verb tense for the sentence describing milk heating:
| Option | Explanation |
|---|---|
| 1. would be | This option is used in the second or third conditional, implying a hypothetical or unreal situation (e.g., "If it were heated, bacteria would be destroyed," suggesting it's not actually heated). It does not fit a general scientific fact. |
| 2. will be | This option is used for future events or the first conditional (e.g., "If it is heated, bacteria will be destroyed," suggesting a specific future instance). It does not represent a constant, universal truth or a general scientific process. |
| 3. is | This is the correct option. When combined with "heated," it forms "is heated," which is the simple present passive voice. This perfectly aligns with the Zero Conditional structure for describing a scientific fact: "when it is heated" (simple present passive for condition) and "bacteria... are destroyed" (simple present passive for result). This correctly states a universal truth about bacteria destruction in milk. |
| 4. was | This option is in the simple past tense. While bacteria *were* destroyed in a past event where milk *was* heated, the sentence is describing a general principle, not a single past event. The main clause "are destroyed" also indicates a present truth, not a past one. |
Conclusion for Sentence Completion
The sentence describes a fixed scientific phenomenon related to milk and bacteria destruction. For such universal truths, the simple present tense is required in both clauses. Therefore, "is" is the only option that correctly forms the simple present passive voice ("is heated") and fits the grammatical structure of the Zero Conditional for scientific facts.
Important Questions from English Grammar
Select the most appropriate 'one word' for the expressions given below
A person who believes in or tries to bring about a state of lawlessness
Select the most appropriate 'one word' for the expressions given below
Urging or requesting (someone) solemnly or earnestly to do something
Four words are given, out of which only one word is spelt correctly. Choose the correctly spelt word.
Select the word segment that substitutes (replaces) the bracketed word segment correctly and complete the sentence meaningfully. Select the option 'no correction required' if the sentence is correct as given.
A natural-born mechanic and tinkerer, (he kept many an old flivver on) the road.
Identify the type of the clause in the brackets.
Our neighbour (who moved in last year) wants to borrow the chainsaw.
