Without seeing your extended response answers all I can offer is a generic scaffold:
(1) Use the blank lines provided to measure the length of your answer.
(2) Answer all parts of the question.
(3) Know the syllabus front-to-back and identify the syllabus points that are being examined in the question.
(4) Note the action verb that is used in order to gauge the degree of synthesis required in your answer (Bloom's taxonomy of learning)
(5) Always avoid re-stating the question in your answer.
(6) get straight to the point - don't waste time writing introductory sentences.
(7) Use the language of the syllabus. Avoid every-day informal language.
(8) Don't be afraid to use graphs, diagrams and mathematical formulae if it improves the accuracy and precision of your answer.