Which of the following elements will produce an oxide that will dissolve in water to form an acid?

The element Z burns in air to form an oxide. The aqueous solution of this oxide turns blue litmus to red. The element Z is most likely to be:

Which of the following element is a metalloid?

The least reactive metal among the following is:

You are given a solution of iron sulphate. Which of the following do you think cannot displace iron from iron sulphate?