Answer:
1. CaO + H₂O ----> Ca(OH)₂
Compound ----- Compound
2. 2 Na + Cl₂ ----> 2 NaCl
Element ----- Element
3. 2 SO₂ + O₂ ----> 2 SO₃
Element ----- Compound
CH4+(x)O2=CO2 +(Y)H2O
C=1 +H=4 +O=? = C=1 +O=2+? +H=?
H=4>>Y=2
C=1 +H=4 +O=? = C=1 +O=(2+2) +H=4
C=1 +H=4 +O=4 = C=1 +O=4 +H=4
O=4>>X=2
CH4+(2)O2 =CO2 +(2)H2O
True is the correct because helio means sun in greek and the sun is in the center of our universe
Answer : (C) "Higher frequencies have larger spaces between lines".
Explanation:
In Young's experiment, the condition for constructive interference is given by :
.........(1)
n is order or number of lines observed
d is distance between slits
is the angle between the path and the line from screen to the slits.
We also know that, 
or

where,
c is the speed of light
is frequency
is wavelength
So, equation (1) turns into


So,

or
Higher frequencies have larger spaces between line.
So, correct option is (C).