Qusजीएसएम (मोबाइल संचार के लिए वैश्विक प्रणाली) विकसित किया गया है?
A. 1970s
B. 1960s
C. 1980s
D. 1990s
Solution
D. 1990sExplanation
Mobile services based on GSM were first launched in Finland in 1991. That same year, the GSM standard frequency band was expanded from 900 MHz to 1,800 MHz.