Which of these is not made up of two or more substances that are combined physically? A. homogeneous mixture
B. compound
C. heterogeneous mixture
D. solution

First to answer will be the brainliest i need the answer asap

Elements in group viiia (also known as group 18, or the noble gases) have similar properties because they all have a. the same number of electron shells b. full octets c. the same number of valence electrons d. the same number of electrons needed to fill their octet

A: all waves on the electromagnetic spectrum travel at the same speed in a vacuum. the speed of these waves in a vacuum is 3x108 m/s. as the wavelength of a wave doubles, how does the speed and frequency of the wave change?