Answer:
The answer is a.
Explanation: Billions of years ago, there were lakes and rivers in the surface of mars because mars had a denser atmosphere and higher surface temperatures which allowed a vast amount of liquid water on the surface. Recently, most of the water on mars today exist as ice.
Answer:
Potassium
k = Potassium
Potassium Has 19 Electrons
the atomic mass is 39.0983
Answer: 258.7 J
Explanation:
Velocity of object V=5m/s
Mass ; 5kg
Height; h=4m
Mechanical energy is equal to sum of kinetic and potential energy
E=K+Ep
Kinetic energy is calculeted using; K=m*V²/2
Potential energy is calculated using : Ep=m*G*h
-------------------------------------------------------------------------
V=5m/s
m=5kg
h=4m
E=K+Ep
E=m*V²/2+m*G*h
E=5kg*(5m/s)²/2+5kg*9.81m/s²*4m
E=62.5J+196.2J
E=258.7 J
Answer:
my favourite song is hym to the sea. That song reminds me of the innocent people who lost their lives in titanic a century ago. If I was the writer of that song ,i would not change the title of that song because I can feel the sound of ocean when I listen to that song.
Answer:

Explanation:
Let r is the radius of the n = 1 orbit of the gold. According to Bohr's model, the radius of orbit is given by :

Where
n = number of orbit
h = Planck's constant
Z = atomic number (for gold, Z = 79)
m = mass of electron
e = charge on electron


So, the radius of the n = 1 orbit of gold is
. Hence, this is the required solution.