You have to do a readback but unless you're familiar with DC geography you might not think to ask which river to follow. You could give the readback correctly a

You have to do a readback but unless you're familiar with DC geography you might not think to ask which river to follow. You could give the readback correctly and then realize you have follow up questions that can't be addressed conclusively by looking at a map. Correct move by that point was ask for clarification even if it made you sound dumb on the radio.