Answer: object B is negatively charged, object C is positively charged and object D is also positively charged
Explanation: since unlike charges attract and like charges repel, for object A which is positively charged and B to attract B must be negatively charged and then for B which is negatively charged and C to attract C must be positively charged and for C and D to repel they have to be of thesame charge which means D is positive as well.
Water vapor and carbon dioxide
the answer is D cuz electricity is a conductive
Answer:

Explanation:
= Vacuum permittivity = 
= Area = 
= Distance between plates = 1 mm
= Changed voltage = 60 V
= Initial voltage = 100 V
= Resistance = 
Capacitance is given by

We have the relation

The time taken for the potential difference to reach the required level is
.