If the T.V's native resolution is greater than or equal to 1,280x720, then the T.V. meets the requirements for HD. As a general rule 37" is considered the breaking point between 720 and 1080. This however is not an absolute.

32" T.V's will mostly be 1366 x 768 resolutions - 768p

You will find that most, not all 46" T.V's will support 1920 x 1080 resolutions - 1080i/p