Researchers working in Western Australia have discovered the oldest fragments of the Earth' s early crust that have yet been identified: microdiamonds. These microscopic crystals measure only 50 microns across and were formed 4. 2 billion years ago. This discovery sheds light on how long it took for the Earth' s crust to form, since this date is only 300 million years after the formation of the Earth itself. If the statements above are true, which one of the following must also be true? ["The Earth's crust first formed in the area that is now Western Australia.", "The Earth's crust took no longer than 300 million years to start to form.", "All naturally occurring microdiamonds were formed at the time the Earth's crust was being formed.", "The Earth's crust took billions of years to form."]