Verb of the Sentence

Machines existed in Leonardo's day.

• existed in

• Leonardo's

• day

• existed

For example, waterwheels turned millstones.

• turned

• turned millstones

• millstones

• waterwheels

As a boy, Leonardo had watched machines closely.

• closely

• had watched

• had

• watched

By adulthood, he had analysed how each part worked.

• had

• analysed

• had analysed

• he had

Unlike others, Leonardo combined parts in new ways.

• combined parts

• combined

• new ways

• others

He thought, "Aha! This change improves the machine!"

• improves

• machine

• change improves

• improves the machine

He reasoned, "This invention is working better with different parts."

• invention

• better

• working better

• is working

He explained his analyses in journals.

• analyses

• journals

• explained

• explained his

Grateful engineers still study his sketches.

• still study

• his sketches

• study

• still

These illustrations are serving as blueprints for us.

• are serving

• are

• serving

• blueprints