When critical altitude is sea level, what is the compression ration for a supercharger gear ratio of 7:1?
CREATE TABLE table_16551 (
    "Engine" text,
    "Power, continuous" text,
    "Critical altitude This is the highest altitude at which the engine can achieve its full continuous power rating. Above this altitude, power falls off with height as with a naturally aspirated engine . See Supercharger#Altitude effects for details." text,
    "Power, takeoff" text,
    "Compression ratio" text,
    "Supercharger gear ratio" text,
    "Octane rating" text,
    "Dry weight" text
)
SELECT "Compression ratio" FROM table_16551 WHERE "Critical altitude This is the highest altitude at which the engine can achieve its full continuous power rating. Above this altitude, power falls off with height as with a naturally aspirated engine . See Supercharger#Altitude effects for details." = 'sea level' AND "Supercharger gear ratio" = '7:1'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: When critical altitude is sea level, what is the compression ration for a supercharger gear ratio of 7:1? ### Input: CREATE TABLE table_16551 (
    "Engine" text,
    "Power, continuous" text,
    "Critical altitude This is the highest altitude at which the engine can achieve its full continuous power rating. Above this altitude, power falls off with height as with a naturally aspirated engine . See Supercharger#Altitude effects for details." text,
    "Power, takeoff" text,
    "Compression ratio" text,
    "Supercharger gear ratio" text,
    "Octane rating" text,
    "Dry weight" text
) ### Response: SELECT "Compression ratio" FROM table_16551 WHERE "Critical altitude This is the highest altitude at which the engine can achieve its full continuous power rating. Above this altitude, power falls off with height as with a naturally aspirated engine . See Supercharger#Altitude effects for details." = 'sea level' AND "Supercharger gear ratio" = '7:1'