Main event of novel DAVID COPPERFIELD from chapter 1 till 5​

You need to start an experiment and the instructions are to mix 2 g of sodium bicarbonate with 50 ml of distilled water and then mix the solution. describe what lab apparatus you would use and what safety precautions you must observe when completing this experiment.

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.

Which sentence is correctly punctuated? a. i haven’t found a new job, and i don’t plan to look for one until i have to. b. my work is piling up—day to day—and i can’t seem to get caught up. c. i know things could be worse (they have been in the past).