A computer system is generally divided into two broad categories: hardware, the physical parts you can touch, and software, the instructions that tell the hardware what to do.
Software is best described as logical sequences of coded instructions. It consists of programs written by developers, made up of ordered instructions in a programming language, which the computer's processor executes to carry out a task. Because it is intangible, software cannot be touched or physically handled the way hardware can; it exists as code stored in memory or on a storage device.
The other options do not correctly describe software. "Elements used for data transmission" and "systems that control data flow" describe communication or networking concepts rather than the general nature of software itself. "Tangible components of a computer" is actually the definition of hardware, the opposite of software, since hardware refers to the physical, touchable parts of a computer system such as the CPU, monitor, or keyboard.
When a definition question asks what software "is", the correct answer will always describe it as instructions or code, since anything described as physical or touchable is describing hardware instead.