Asking a multiple choice question without providing the choices doesn't really seem fair.
Yes, it is a common noun.
[object Object]
[object Object]
A common object that is an octagon is a "stop sign".
[object Object]
You can catch them all.
A common lever is used to move an object
A common object that is approximately 25cm in size is a standard ruler.
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[object Object]
To find the mass of an irregular object using a common balance, you can first weigh a known object with a regular shape to calibrate the balance. Then, weigh the irregular object. Subtract the mass of the known object from the total mass to determine the mass of the irregular object.
In this sentence the common noun frog is the direct object of the verb 'caught'.