Answer:
Es segura.
Explanation:
I´m going to explain this answer in two parts. First I will focus on the adjective: segura (safe) and then on the conjugation of the verb: es (is).
In Spanish motocicleta (motorcycle) is a singular feminine noun, so the adjective that qualifies it, in this case, segura must also be written in feminine. With this in mind, two options are ruled out: es seguro and está seguro, because both of them allude to masculine nouns (notice that they end in -o, unlike the feminine ones that end in -a).
Now let´s see the hardest part, why do you say es segura rather than está segura? Remember that the verb "to be" in Spanish has two meanings: ser and estar. Ser is used when you want to talk about a property (let's call it permanent) of an object or person. Estar refers only to (temporary) situations that may change at any time. In our case, segura is a property that is detected by the interlocutor as permanent: That motorcycle is not safe and, as it is by nature, he is afraid to ride it.
