Detailed Instructions: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Q: Question: Why does carbenicillin have a low antibacterial activity by mouth ?:
Options: <1> It is degraded by beta-lactamases in the digestive system. <2> He undergoes first-pass hepatic oxidative metabolism. <3> It binds covalently to plasma proteins. <4> It is decarboxylated in the acid medium of the stomach giving rise to benzylpenicillin, which is also unstable in that medium. <5> It is highly lipophilic, which is why it is not released correctly from oral administration forms.
A:
4