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The four types of waves mentioned in the given exercise are: 1. Infra red (IR): These are electromagnetic waves with longer wavelengths than visible light but shorter than microwaves. They are typically used for remote controls, thermal imaging, and night vision equipment. 2. Visible light: These are electromagnetic waves that humans can see, having wavelengths in the range of approximately 400-700 nanometers. They are not generally used for telecommunication purposes, but rather for vision. 3. Microwaves: These are a type of electromagnetic wave with wavelengths ranging from one meter to one millimeter. Microwaves are used for a variety of applications, including heating in microwave ovens and wireless communication. 4. Ultraviolet rays: UV rays are electromagnetic waves with wavelengths shorter than visible light but longer than X-rays. They can cause damage to living organisms, and are typically not used for telecommunication purposes.

From our understanding of the different types of waves in Step 1, we know that microwaves are used for various applications, including wireless communication. Thus, the correct answer for the waves related to telecommunication is: (C) Microwaves