Poor students want to start with SLR, which one should Sony a29, Canon 45d and Nikon d7 choose?

If the landlord is a beginner in photography and plans to study SLR in the future, he will buy Nikon D7, which has all the basic functions. Even compared with today's entry-level SLR, it is not backward. The shoulder screen, body motor and double impeller are only available in the mid-range machine now. The picture quality of 6 million pixels (for playing with 12-inch photos) is very high, and the body feels good (absolutely bright), and the second-hand one is within 2, shutters. Bisogni a29 and Canon 45D are much more practical! PS: With a Nikon 5mm1.8D, experience the charm of large aperture, 7 yuan! Nikon's cheapest fixed focus, scenery and portraits can be inserted! Hope to adopt