I think it is best if there are two different samples that will be retrieved from the person to ensure that the first sample that was taken will not be contaminated. This explains why in getting blood and urine samples, the samples would depend on the number of tests that will be done. If the urine would need to be tested for routine urinalysis and culture then two samples should have been taken.
The answer to this is letter B. The urine may already be rejected because of its contamination with the first test. There are times when the culture and urinalysis will be processed by two different labs so there is no reason why they cannot be done at the same time if there are two different samples.