You have two kidneys, each about the size of a fist, located on either side of the spine at the bottom of the rib cage. Each kidney contains about one million functioning units called nephrons. A nephron consists of a filtering unit of tiny blood vessels, called a glomerulus, which is attached to a tubule. When blood enters the glomerulus, it is filtered and the remaining fluid then passes through the tubule.
In the first case, each time the computer starts up, the question mark appears and flashes for a few seconds, then disappears. The cause of this symptom is that there is no hard drive selected in the Startup control panel. Remember that selected on the Macintosh means that an icon is darker than the other.
To flicker is to flash on and off at random. If your computer screen is flickering right now, you are probably having trouble reading this. Something that is flickering is flashing on and off in an unpredictable way. A fluorescent light may flicker for a while before it stops working. A flicker is also a quick flash or burst of light, like a glint or a spark. Similarly, flicker can refer to a sudden and short-lived feeling. A child opening a present might have a flicker of excitement before realizing that the box contains only tube socks and underwear.