This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Well, if the four abstract classes themselves formed an inheritance hierarchy -- i.e., A extends B, B extends C, C extends D, and A-D are all abstract classes, then you could extend A, this making the answer "true". Without more context, it's hard to say what the "right" answer is.