They carry opposite types of charges.
Explanation
The interaction between electrically charged bodies is governed by the fundamental laws of electrostatics. These laws dictate the nature of the force (attraction or repulsion) based on the polarity of the charges involved.
Detailed Analysis:
- They carry the same type of charge. is Incorrect: If two objects carry the same type of charge (both positive or both negative), the electrostatic force between them is repulsive. They would push away from each other rather than attract.
- They carry opposite types of charges. is Correct: According to the fundamental law of electric charges, unlike (opposite) charges attract each other. Since the question explicitly states that both the glass rod and the plastic straw are charged and that they attract each other, they must possess opposite polarities (one positive and one negative).
- One is charged and the other is neutral. is Incorrect: While it is true that a charged body can attract a neutral body due to the phenomenon of electrostatic induction, the plastic straw is "charged." Therefore, the attraction is strictly due to the interaction between opposite charges.
- Both objects are electrically neutral. is Incorrect: If both objects were electrically neutral, there would be no electrostatic force acting between them.
Key Takeaway:
Like charges repel, and unlike charges attract. While attraction can occur between a charged body and a neutral body (induction), attraction between two bodies known to be charged implies they carry opposite charges.