past tense,present tense,past participle

问题描述:

past tense,present tense,past participle
Is this correct?
1)Past tense
The demand for energy dropped steadily between 1985 and 1990 from 5 units of energy to approximately 2 units.
2)Present tense
The demand for energy dropps steadily between 5 units of energy to approximately 2 units.
3)past participle
The demand for energy has dropped steadily between 1985 and 1990 from 5 units of energy to approximately 2 units.
or
4)The demand for energy has dropped steadily from 5 units of energy to approximately 2 units.

我觉得pp比较合适