Nucleoplasmin is a nuclear protein. This protein was divided into two segments and linked to the same large cytoplasmic protein, generating two fusion proteins. After injecting these fusion proteins into a cell, one of the proteins was found in the nucleus and the other in the cytoplasm. Which of the following conclusions can be drawn from these results?1. The cytoplasmic protein contains a nuclear localization signal.2. Nucleoplasmin does not have a nuclear localization signal.3. One of the fusion proteins entered the nucleus by passive transport.4. Only one of the two fusion proteins possesses a nuclear localization signal.