OPTION 3 i.e. Import of varieties of product.The above passage is about intra-industry trade.Let us REFER to this line from the passage, "With few varieties and styles, more specialised and faster machinery can be DEVELOPED for continuous operation and a longer production run. The nation then imports other varieties and styles from other nations."From the above line, we get to know that as industrial countries produce only one type of same product so specialised and after machinery will help them to produce new varieties of products and import new varieties and styles.From the above lines, we can infer that DEVELOPMENT and use of specialised machinery will lead to the import of varieties of product.