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The fact has worried many scientists ______ the earth is becoming warmer and warmer these years. 

A. what          B. which         C. that       D. though 

The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

A. what          B. which         C. that       D. though

 The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

A. what              B. which             C. that              D. though

The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

A. what          B. which         C. that       D. though

The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

A. what          B. which         C. that       D. though

The fact has worried many scientists _____ the earth is becoming warmer and warmer these years.

The fact has worried many scientists ________the earth is becoming warmer and warmer these years.

A．what           B．which            C．that                     D．whose

The fact has worried many scientists _____ the earth is becoming warmer and warmer these years.

A．which            B．that              C．a(chǎn)s               D．what

The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.