If more than 50% of their sales volume is from generic drugs, which of the following options is definitely correct?
(Note : All percentages figures are with respect to total sales volume)

Option D is the correct answer. Let us examine the choices individually:

Option A: [Incorrect] [If the sales volume of patented drugs in India is 43%, the sales volume of generic drugs in India will be less than 43%.]

We can create the following 2*2 matrix to process the data [note: text in red = given information; text in blue = required value]

It is evident that the sales volume of generic drugs in India will be less than 7% (and not 43%) [For instance, the value cannot be 40% but instead must be below 7%]

Option B: [Incorrect] [If the sales volume of generic drugs in foreign countries is at least 24%, the sales volume of patented drugs in India will be above 24%.]

It is evident that the sales volume of patented drugs in India will be below 24%.

Option C: [Incorrect] [If the sales volume of patented drugs in India is 54%, the sales volume of generic drugs in foreign countries will be above 54%.] 

The instructions specify that the sales volume in India is below 50%; therefore, the sales volume of patented drugs in India must also be below 50% (i.e. it cannot take the value specified in the option)

Option D: [Correct] [If the sales volume of patented drugs in India is 29%, the sales volume of generic drugs in foreign countries will be above 29%]

It is evident that the sales volume of generic drugs in foreign countries will be above 29%

Option E: [Incorrect] [If the sales volume of generic drugs in India is at least 60%, the sales volume of patented drugs in foreign countries will be above 60%.]

The instructions specify that the sales volume in India is below 50%; therefore, the sales volume of generic drugs in India must also be below 50% (i.e. it cannot take the value specified in the option)