How to use @InjectMocks along with @Autowired annotation in Junit

It should be something like

@RunWith(SpringJUnit4ClassRunner.class)
public class aTest () {

    @Mock
    private B b;

    @Mock
    private C c;

    @Autowired
    @InjectMocks
    private A a;

}

If you want D to be Autowired dont need to do anything in your Test class. Your Autowired A should have correct instance of D.
Also i think you need to use SpringJUnit4ClassRunner for Autowiring to work, with contextConfiguration set correctly.
Because you are not using MockitoJunitRunner you need to initialize your mocks yourself using

MockitoAnnotations.initMocks(java.lang.Object testClass)