Hi. Are these correctly punctuated? Are there valid reasons for there being a comma in one (number i sentence) and not in others?<br/><br/>1.Until the 1900<u>s, </u>what is now known as XXX was dry land.<br/><br/>2.During the 1600<u>s </u>people from other places began coming there.<br/><br/>3.In climates with cold sno<u>w </u>they hibernate.<br/><br/>4.In very cold climate<u>s </u>they stay inside at night.