Understanding Voice in English Grammar

In English grammar, voice refers to the relationship between the verb and the subject. There are two main voices:

• Active Voice: The subject performs the action of the verb. Example: Birds build nests. (Birds are doing the building)
• Passive Voice: The subject receives the action of the verb, or the action is performed upon the subject. Example: Nests are built by birds. (Nests are receiving the action of building)

Converting Active to Passive Voice with Modal Verbs

The given sentence is "Animals cannot make tools." This sentence is in the active voice because the subject, "Animals," is performing the action, "cannot make." The object of the action is "tools."

The sentence includes a modal verb, "cannot." Modal verbs are auxiliary verbs that express possibility, necessity, permission, or ability (like can, could, may, might, must, shall, should, will, would). When converting an active sentence with a modal verb to the passive voice, we follow a specific structure:

Active Structure: Subject + Modal Verb + Base Verb + Object

Passive Structure: Object (becomes new subject) + Modal Verb + be + Past Participle of Main Verb + by + Subject (becomes new object)

Step-by-Step Conversion of "Animals cannot make tools"

Let's apply the rules to transform "Animals cannot make tools" into the passive voice:

1. Identify the Subject, Verb, and Object:
   • Subject: Animals
   • Modal Verb: cannot
   • Base Verb: make
   • Object: tools
2. Move the Object to the Subject Position: The new subject of the passive sentence will be "tools".
3. Keep the Modal Verb: The modal verb "cannot" remains the same.
4. Add "be" after the Modal Verb: We add "be" after "cannot".
5. Use the Past Participle of the Main Verb: The past participle of "make" is "made".
6. Add "by" and the Original Subject: We add "by" followed by the original subject, "animals".

Combining these steps, the passive form is:

Tools + cannot + be + made + by + animals

Resulting Passive Sentence: Tools cannot be made by animals.

Analyzing the Options

Now let's look at the provided options and compare them with our derived passive sentence:

• Tools could not be made by animals. - This option changes the modal verb from "cannot" to "could not," altering the meaning slightly (from present inability to a past possibility or general statement about ability). It's not a direct passive transformation of the original sentence.

• Tools cannot be made by animals. - This option perfectly matches the passive sentence we derived using the correct rules for modal verbs. It retains the modal verb "cannot."

• Animals cannot be made by tools. - This sentence incorrectly swaps the subject and object and completely changes the meaning. It implies tools are making animals, which is not the passive form of the original sentence.

• Tools are not to be made by animals. - This structure ("are not to be made") implies a command, prohibition, or arrangement, which is different from the simple statement of inability expressed by "cannot make." It is not the correct passive transformation.

Based on our analysis, the correct passive form of "Animals cannot make tools" is "Tools cannot be made by animals."

Revision Table: Active vs. Passive Voice with Modals

Additional Information: Uses of Passive Voice

The passive voice is used in English for various reasons:

• When the doer of the action (the agent) is unknown, unimportant, or obvious from the context.
• When you want to emphasize the action or the receiver of the action rather than the doer.
• In scientific or technical writing, to maintain objectivity.
• When reporting events in news articles where the focus is on what happened.

In the sentence "Tools cannot be made by animals," the focus shifts from the animals' inability to the tools and their state of not being able to be made by animals. While the agent ("by animals") is included, the structure emphasizes the object "tools".