choose the grammatically incorrect sentence.

a.

when we were touring san francisco, i was disappointed to see that the golden gate bridge was actually rusty red, not glittering gold.

b.

i tried to explain to the canadian fisherman that he should go into the water at miami beach since it was actually warm.

c.

the country was slipping into another depression, so i decided to boost the economy with a major shopping spree at target.

d.

i hate flying, but i will made an exception if i ever get the opportunity to travel to antarctica because it's my dream vacation spots.

a, a knight

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.