A RUN-ON SENTENCE has at least two parts, which can stand on their own (in other words, two independent clauses), but the two parts have been squashed together instead of being properly connected.

 The sun is high, put on some sunblock. Each part of this sentence makes sense of its own so it is two separate clauses. This is called a comma splice. You either need to add a full stop: The sun is high. Put on some sunblock. Or add a connective: The sun is high so put on some sunblock.

1. The old man rushed down the street he walked into the chip shop and asked for a burger. 2. Ice cream melts in the sunlight it is not a good idea to leave it out of the fridge. 3. Smoking is not good for your health our lungs were not designed to breath in smoke. 4. Last week we went to a concert my sister got lost in the crowd it was so embarrassing.

1. The old man rushed down the street. He walked into the chip shop and asked for a burger. 2. Ice cream melts in the sunlight. It is not a good idea to leave it out of the fridge. 3. Smoking is not good for your health. Our lungs were not designed to breath in smoke. 4. Last week we went to a concert. My sister got lost in the crowd. It was so embarrassing.