Can come down to C and D

Now D, a very tempting one, has no support from the data in the argument. You don't have a base for this statement. The increased TV may be coz of the increased demand in that country or increase in efficiency ! We don't have enough data to support the export point!

C - Very nicely worded. It just means that "The efficiency of workers has remained the same". The number of TV sold is also constant. So, basically, if the efficiency decreases the number should go down. But, It is not going down here. It is remaining the same as before. It is possible only with an import from the other country !

Maybe a simpler way of approach this is to start by summarizing the argument, then looking for a gap.

P: TV assemblers in Borodia aren't paid as much per hour as TV assemblers in Vernland.
P: The number of TV assemblers in Borodia has dropped. (Shocking! )
P: The number of imported Vernlandian TV's sold in Borodia hasn't changed over the past three years.
C: Nonetheless, Borodia will probably soon be importing more TV's from Vernland.

One way to find the gap is to try to find the justification connecting the premises to the conclusion. (I usually do this by trying to talk the argument out in everyday terms.) In this question, we go from "there are fewer TV assemblers in Borodia" to "there will presumably be a shortage of Borodian made TV's, forcing Borodia to import TV's from Vernland". Well, who says that fewer assemblers means fewer TV's? Sounds like an assumption! So the best answer is anything that says something along these lines ... and you know the right answer by now.

Quick aside: you're right that this is a tough question, but it's mostly tough because there are so many worthless premises to work around. The basic argument is "Nobody wants to make a TV in Borodia because the pay there sucks, so Borodia will have to start importing TV's."