Which one of the following roles is not characteristic of an essential element?

Which one of the following roles is not characterstic of an essential element?

Which of the following is not a characteristic of transition elements?

Which of the following is not a characteristic of transition elements ?

Which one of the following is 'Arnon's criterion for essentiality' of element?

Which one of the following is not a criteria for essentiality of an element according to arnon and stout?

Which one of the following is not a criteria for essentiality of an element according to arnon and stout?

Which of the following are the characteristics of isotopes of an element ?