I need ur help guys.
I'm really confused that why the answer is E??
Can someone explain this for me with some detail info??
I'd appreciate it. Thanks.

E. BeH2, BH3, CH4 are non polar how come?

Is it because BeH2 have 180 linear form that cancel out the dipole moment,
BH3 also same since they have 120
and CH4 as well for 109.5 which all cancels their dipole and no net dipole.

You have to look at the geometry of the molecules to understand this question. Polarities only occur if there are differences in electronegativities of atoms in a molecule AND if the vectors do not sum to zero!

BeH2: I "believe" Be makes 2 bonds. Being that it makes two bonds the two hydrogens will be oriented as far away from each other as possible. Given that, that means that their vector sum will be zero b/c they're of equal magnitude and opposite direction.

BH3: Same thing, B makes 3 bonds.

CH4: Same thing, C makes 4 bonds.

If you had, say, BH2Cl then there WOULD be a dipole b/c the vector sum would not be zero. So, yes, it is exactly why you think it is.

H is more electronegative than Be. Because of the symmetry of the molecule. however, the vector sum of these polar dipoles is zero.

H is more electronegative than Be. Because of the symmetry of the molecule. however, the vector sum of these polar dipoles is zero.

Why is H more electronegative than Be?????

Why is H more electronegative than Be?????
That's beyond the scope of the DAT, IMHO. The important thing to know is that it doesn't follow the column trends that the other elements do.

okay this will be much easier if you can see a drawing

By the way, be careful. non polar does not mean it does not contain polar bonds but rather the dipole moments of polar bonds are cancelled due to pointing out to same direction (or it could be simply non-polar bonds too)

BeH2
Be has 2 valence electron and H has 1, so it would be total of 2 + 2 (1 from each H) = 4 valence electrons.

H-Be-H

would be something like the picture with no non-paired electrons.
Be and H's electronegativity difference is about 0.6 which makes this polar bonds (H being more electronegative) but since both will be pointing out to each ends, they will cancel out each other and thus be non polar.

BH3
B has 3 valence electrons and H each has 1 (so multiply by 3) = you have 6 valence electrons.

now B being in the center and H will be around B in equal degree (120 degree since it would be sp2 hybridized). B and H's electronegativities are very similar (with difference of 0.1, H being more electronegative).

so this molecule would be simply non-polar, and even if the e- negativity difference was big enough to be a polar bond (but smaller than ionic bond); it would still be non polar molecule since they will cancel each others out.

CH4
methane is non-polar and you should know it w/o hesitation. Carbon and Hydrogen's electronegativity difference is about 0.4, it already falls under non-polar bonds. even if they were polar bonds, four H's being on each of tetrahedral will cancel each others out and be non-polar.

hope this helps

You have to look at the geometry of the molecules to understand this question. Polarities only occur if there are differences in electronegativities of atoms in a molecule AND if the vectors do not sum to zero!

BeH2: I "believe" Be makes 2 bonds. Being that it makes two bonds the two hydrogens will be oriented as far away from each other as possible. Given that, that means that their vector sum will be zero b/c they're of equal magnitude and opposite direction.

BH3: Same thing, B makes 3 bonds.

CH4: Same thing, C makes 4 bonds.

If you had, say, BH2Cl then there WOULD be a dipole b/c the vector sum would not be zero. So, yes, it is exactly why you think it is.

This explanation is great. Just think of each individual bond dipoles as vectors, and if they're all equal, then the total vector sum is 0, which means no molecular dipole. And that's what you need for polarity. Think of water. the 2 O-H bonds have bond dipoles, but based on their orientation, you have the a molecular dipole with the (-) on O and (+) on H. Therefore, with the molecular dipole, water is polar.