The correct answer is option 'A', i.e., 220 V a.c.

Explanation:
Electricity can be transmitted in two forms - AC (alternating current) and DC (direct current). Both forms of electricity can be dangerous but the level of danger depends on various factors such as voltage, current, resistance, frequency, and duration of exposure.

Let's understand why 220 V a.c. is more dangerous than 220 V d.c.:

1. Effect on the human body:
- AC current alternates its direction of flow and causes muscle contractions and spasms, making it difficult for a person to let go of the source of electricity. This increases the risk of electrocution and can be fatal.
- DC current flows in one direction and causes muscle contractions and spasms but it is easier to let go of the source of electricity.

2. Frequency:
- AC current has a frequency of 50 or 60 Hz, which means it alternates its direction 50 or 60 times per second. This rapid change in direction makes it more dangerous and can affect the heart rhythm.
- DC current has a frequency of 0 Hz, which means it flows in one direction only and does not affect the heart rhythm.

3. Appliances and devices:
- Most household appliances and devices run on AC current, which means the chances of coming into contact with AC electricity are higher.
- DC current is mainly used in batteries, electronic devices, and some industrial applications.

Therefore, based on the above factors, it can be concluded that 220 V a.c. is more dangerous than 220 V d.c. However, it is important to note that both forms of electricity can be lethal and should be handled with caution. It is recommended to always turn off the power source before working on electrical equipment and to wear protective gear.