Buona fortuna amici!!!
my sis just took the test the answer is
B.) An atom is solid material.
or An atom is a solid sphere.
The correct answer to the question is : B) An atom is a solid material.
From Rutherford's alpha ray scattering experiment, we know that most of the spaces in an atom is empty.
It is so because most of the alpha particles in that scattering experiment had gone undeviated without any deflection by the positively charged nucleus.
Hence, atom can not be considered as a compact solid sphere.
The answer is a few seconds since it is closed but the water drains after 3-5 seconds.
I took the test. BAM!