The oldest tool view passage image the hammer may be the oldest tool we have record of. stone hammers—some of the oldest human artifacts ever discovered—date back as early as 2,600,000 bce. not only is the hammer the oldest tool, but it is also the greatest. what makes the hammer so great is its simplicity, power, and usefulness. the structure of the hammer is relatively simple, a fact largely responsible for its early invention and widespread distribution across cultures and geographic regions. the hammer is composed of two main parts: a handle and a head. the handle is used to swing the hammer. the head is used to hit other objects. while the hammer is a very simple tool, it is still able to generate tremendous power. this power results from two factors: the weight of the head, and the speed at which the hammer is swung. every hammer (though some more than others) has a large distribution of weight at the head. when a hammer is swung, this weight pivots about the hand, which acts as a fulcrum. the handle carries the weight at a distance, acting as a lever arm, so a longer handle means increased speed. the weight of the head together with the speed generated by the lever arm is what gives the hammer so much power. the heavier the head and the faster it is swung, the more power a hammer produces. in addition to the hammer's great power, it also has an exceptionally wide range of useful applications. the purpose of the hammer—to hit—is a universal action that can accomplish many tasks. let's start with the obvious: a hammer can be made to pound nails. but a hammer has many other uses as well. it can break apart hard objects such as brick or concrete. it can bend and shape metal or steel. it can gently tap objects to make small adjustments. it can be used to make sculpture or pottery. it can be used in the hot, harsh business of blacksmithing as well as in delicate operations like crafting jewelry. in times of desperation, it can even be used as a weapon. the hammer truly is a great tool. it is simple, powerful, and useful. a quintessential symbol of labor, the hammer has come to represent hard work and embody the spirit of human industry.

the thesis statement is one sentence that clearly communicates what the author plans to discuss in the passage. based on this information, which of the following sentences from the passage is its thesis statement?
a. "the hammer may be the oldest tool we have record of."
b. "not only is the hammer the oldest tool, but it is also the greatest."
c. "a quintessential symbol of labor, the hammer has come to represent hard work and embody the spirit of human industry."
d. "what makes the hammer so great is its simplicity, power, and usefulness."