Which of the following statements is/are found to be correct regarding the town planning of the Indus Valley Civilization? I. Indus cities were all built of bakedbrick blocks with standard proportions of length to width to thickness of 4:2:1, except along the Makran coast. II. The citadel was divided into a number of blocks by a grid of straight streets running north-south and east-west. III. Mohenjodaro and some other Indus cities consisted of two sectors, a western citadel and an eastern lower city.