Which of the following experimental results from BbTt x bbtt crosses
indicates probable gene linkage?

A. 1 BbTt, 7 Bbtt, 7 bbTt, 1 bbtt
B. 4 BbTt, 4 Bbtt, 4 bbTt, 4 bbtt
C. 7 BbTt, 1 Bbtt, 1 bbTt, 7 bbtt
D. BbTt, 1 Bbtt, 7 bbTt, 1 bbtt