In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select 'No Error'.
I was taken by surprise (A)/when I came(B)/face to face with my school friend.(C)/No error(D)
In a market system, the central problems regarding how much and what to produce are solved through the coordination of economic activities brought about by ________ signals.