**Core Concept**
The Roll Back Malaria (RBM) programme is a global initiative to control and eventually eliminate malaria. It focuses on reducing the burden of malaria through a combination of strategies, including vector control, early diagnosis, and treatment.

**Why the Correct Answer is Right**
The RBM programme has primarily emphasized the use of insecticide-treated bed nets (ITNs) as a key intervention for preventing malaria. ITNs work by preventing mosquitoes from feeding on individuals, thereby reducing the transmission of malaria parasites. The World Health Organization (WHO) and other global health authorities have recommended the widespread use of ITNs as a cost-effective and highly effective measure for controlling malaria.

**Why Each Wrong Option is Incorrect**
**Option A:** IEC campaigns for community awareness are an important component of public health programmes, but they are not the primary focus of the RBM programme. While community awareness is crucial for promoting the use of ITNs and other malaria control measures, it is not the main strategy employed by the RBM programme.
**Option C:** Development of larvivorous fishes for eradication of larvae is a biological control method that has been explored for malaria control. However, it is not a primary focus of the RBM programme, which has concentrated on vector control measures such as ITNs and indoor residual spraying (IRS).
**Option D:** Presumptive treatment of malaria cases is an important aspect of clinical management, but it is not the main focus of the RBM programme. The RBM programme has emphasized the importance of early diagnosis and treatment, but it has not prioritized presumptive treatment as a primary strategy.

**Clinical Pearl / High-Yield Fact**
The RBM programme has been instrumental in increasing the coverage and availability of insecticide-treated bed nets, which has resulted in a significant reduction in malaria cases and deaths worldwide. Students should remember that ITNs are a cornerstone of malaria control efforts and are recommended by global health authorities as a primary intervention for preventing malaria.

**✓ Correct Answer: B. Insecticide treated bed nets**