Question

Future perfect they will have mowed all the grass.​

Answer 1

A lawn mower is a machine utilizing one or more revolving blades to cut a grass surface to an even height. The height of the cut grass may be fixed by the design of the mower, but generally is adjustable by the operator, typically by a single master lever, or by a lever or nut and bolt on each of the machine's wheels.

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Answer 2

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They will have moved all the grass.

Yes ,it is a Future Perfect Tense.

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The future perfect is a verb form or construction used to describe an event that is expected or planned to happen before a time of reference in the future,

For example:- "I will have finished by tomorrow."

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