What is the main difference between a spiral galaxy and a barred spiral galaxy?

a. whether it has barred arms of stars surrounding the nucleus

b. whether there are bars of dark matter stretching across the galaxy

c. whether it has a central "bar" of stars rather than a rounded nucleus

d. whether there are barred sections of the halo, which do not form spirals

Biology 1c cumulative exam i need awsners

Which organisms have pharyngeal arches that develop from all three germ layers and go through the same development stages as embryos? 1.bird 2.ladybug 3.starfish 4.snake

Recent research by marine biologists suggests that bottlenose dolphins have names for themselves. scientists played sounds they had identified as the names of particular dolphins, putting them through a synthesizer so that they did not sound like the voices of particular dolphins. the researchers found that dolphins would respond to the names of other dolphins that they were related to or associated with, but they ignored the names of strangers. this discovery suggests a much greater degree of self-awareness in aquatic mammals than was previously suspected. if this research holds up, what does it suggest about dolphins?