Identify the element in urea that makes it an organic compound

According to the tide table below what time of day will the highest tide occur?

Can someone me with 1 to 4 plz. fast

Astring vibrates with a frequency of 10 hz. why can't a person hear the sound waves produced by the vibrating string, no matter how large the amplitude of the waves? out! this is homework and due tomorrow! you so much!