A substance that vigorously reacts with most metals to produce hydrogen, readily conducts electricity, turns litmus red, and has a pH less than 7; typically corrosive or sour-tasting. A: suspension
B: base
C: acid
D: colloid

C. Acid

Explanation:

If you have chemistry classes and performed experiments regarding acids and bases, you would physically tell it's acid if the lithmus paper turned red and base if it turned blue. Also, in the pH level chart, there are only two characteristics--acidic and basic. Since it has less than 7 pH, it is definitely acid. Plus, remember the taste of some vitamin C tablets? It has a sour taste to it, isn't it? This is because of ascorbic acid.

c. 7/3

step-by-step explanation:

a rational number is like pi- it is a repeating decimal.

a. is -1.8

b. 2.236068

c. 2.3333333333333333333

d.   is 3

i hope that ! =)

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.