What is a tornado? A
a sensor that measures wind speed, temperature, pressure, and direction
B
a first-floor room without windows in the middle of a house
С
a person who studies winds and shares his or her findings with others
spinning wind that forms a funnel and can cause a lot of damage

D!!

spinning wind that forms a funnel and can cause a lot of damage

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

tom robinson he was a black man that was accused of raping caucasian woman, and an idealistic lawyer offers to defend him. which makes nobody believe in the innocence of a negro.