Find out which underlined part of the following sentences has an error. Mathematics is "harder" to most "students", but "practice" makes "perfect"."No Error"

Global "warmth" "have" become a serious matter for the "survival" of "mankind". "No Error"

Since "erect" in 1886, the Statue of Liberty "has served" as "a" symbol of "freedom". "No Error"

Fiber "is important" element "in" nutrition and it aids in "protecting" the digestive "tract" as well. "No Err...

Voyager 2 is a spacecraft "which" has "greatly" expanded "us" knowledge "of" the solar system. " No Error" "No...

"Many " opinions have been "voiced" on the likely "effective " of the effective.

Passive smoking is "defined" as the "exposure" of "nonsmoker" to "environmental" tobacco smoke.