(2) Indo-China Peninsula D, which is characterized by high terrain in the north, delta plain where rivers enter the sea in the south, and mountains and rivers extend from north to south, forming a columnar distribution of mountains and rivers;
(3) Southeast Asia is an important production base of hot crops in the world, among which Thailand is the world's largest producer of natural rubber and the Philippines is the world's largest producer of coconut.
(4) The strait north of Island A is the Straits of Malacca, which is very important for the future of China. The reason is that with the rapid development of China's economy, oil imports will increase rapidly, and the Malacca Strait is the only place for China to import oil by sea.
So the answer is:
(1) Sumatra Island; Tropical rain forest climate; Kuala Lumpur;
(2) The terrain in the north is high and steep, where the rivers in the south enter the sea are delta plains, and the mountains and rivers extend from north to south, forming a situation in which mountains and rivers alternate with each other and are distributed in columns;
(3) tropical; Thailand; Philippines;
(4) With the rapid development of China's economy, the import of oil will increase rapidly, and the Malacca Strait is the only place for China to import oil by sea.