2) chemical
3) chemical
4) physical
5)chemical
6)chemical
7)physical
8)physical
9)physical / chemical
100% sure
A four cycle engine works with 4 basic steps to a successful rotation of the crankshaft: the intake, compression, power and exhaust stroke. Each engine cylinder has four openings for the intake, exhaust, spark plug and fuel injection. ... The compression makes the air-fuel combination volatile for easier ignition.
Explanation:
Relation between pressure, latent heat of fusion, and change in volume is as follows.

Also, 
where,
is the difference in specific volumes.
Hence, 
As,
= 22.0 J/mol K
And,
...... (1)
where,
= density of water
= density of ice
M = molar mass of water =
Therefore, using formula in equation (1) we will calculate the volume of fusion as follows.
=
=
Therefore, calculate the required pressure as follows.

=
or, = 145 bar/K
Hence, for change of 1 degree pressure the decrease is 145 bar and for 4.7 degree change dP =
= 681.5 bar
Thus, we can conclude that pressure should be increased by 681.5 bar to cause 4.7 degree change in melting point.
I think the correct answer would be D. The reaction that involves an acid and a covalent base would be the reaction of sulfuric acid and water or H2SO4 + 2H2O → 2H3O+ + SO42– . The acid would be H2SO4 and the covalent base would be H2O since it is being held by covalent bonds and when in solution it will have equal amounts of OH- and H+ ions.