Which of the following halides is the best to prepare Grignard reagent?

Which of the following acids cannot be prepared from Grignard reagents?

Which of the following acids cannot be prepared by Grignard reagent?

Which of the following metal is used in the preparation of Grignard's reagent?

Which of the following alkyl halides on conversion into the Grignard reagent followed by treatment with water would yeild 2-methylbutanae