Final answer:
Increasing Echo Train length decreases SNR due to signal division.
Step-by-step explanation:
As you increase the Echo Train length, the SNR decreases because the signal strength is divided among a greater number of echoes.
SNR stands for Signal-to-Noise Ratio, which is a measure of the strength of the signal compared to the background noise.
When the Echo Train length is increased, more echoes are acquired, resulting in a reduction in the SNR.