Boost and Virgin are owned by Sprint, which run on the Sprint CDMA network. There's no GSM network for any of them. Verizon is the other carrier with a separate CDMA network. T-Mobile and AT&T each have their own GSM networks.
ETD means that the Eustachian tube is blocked or does not open properly. Air cannot then get into the middle ear. Therefore, the air pressure on the outer side of the eardrum becomes greater than the air pressure in the middle ear. This pushes the eardrum inward.
The Eustachian tube helps the frog to bring in sound and to hear. The eustachian tube of a frog equalizes the pressure of the inner ear by opening and closing, which aids with sound and hearing. They help to balance the frog. The Eustachian tubes also lead to the eardrums. Or.... instead so its simpler to remember the most important function of the frogs Eustachian tube is that... It was mainly used for equalizing pressure in the inner ear while the frog is swimming. It equalizes the pressure of the frog's inner ear while it's swimming.