In a room, there is a magical plant called the Fidelis Fern, which has a unique property: it becomes invisible when only dishonest people are present. One day, three friends--Keiji, Amina, and Gustavo--are standing in the room with the Fidelis Fern. Keiji can see the plant, but Amina and Gustavo cannot. When Keiji leaves the room, suddenly Amina can see the Fidelis Fern, but Gustavo still cannot. What does this tell us about the honesty of Keiji, Amina, and Gustavo?

Provide a brief response.
The Fidelis Fern's magical property is the key to understanding the situation. When Keiji is in the room with Amina and Gustavo, he can see the fern, indicating that there is at least one honest person among them, and since Amina and Gustavo cannot see the plant, they must both be dishonest as they cannot see it unless an honest person is present. The act of Keiji leaving the room tests a different scenario; Keiji's departure leaves Amina and Gustavo alone with the plant. Now, if Amina can see the plant after Keiji leaves, this tells us that an honest person is present in the room. Consequently, Amina must be honest, and her ability to see the Fidelis Fern indicates a change in the presence of honesty in the room. Since Gustavo still cannot see the plant even after Keiji leaves and Amina can, he must be the one who is dishonest. Therefore, Keiji and Amina are both honest, and Gustavo is dishonest.