In BF3 there is back bonding in between fluorinc and boron due to presence of p-orbital in boron. Back bonding imparts double bond characteristics . As BF3 forms adjust the back bonding is no longer present and thus double bond characteristic disappears. Hence, bond become a bit longer than earlier (1.30 A)..

So, correct answer is "greater than 1.30 A"...

¶¶Hope it's help...¶¶

B-F Bond Length in BF3
The B-F bond length in BF3 is 1.30Å (angstroms). This means that the distance between the boron (B) atom and the fluorine (F) atom in the BF3 molecule is 1.30Å.

Adduct Formation
When BF3 is treated with Me3N (trimethylamine), it forms an adduct called Me3N-BF3. In this adduct, the trimethylamine molecule coordinates with the boron atom in BF3 through a coordinate bond.

B-F Bond Length in Me3N-BF3 Adduct
The bond length of B-F in the Me3N-BF3 adduct can be different from the B-F bond length in BF3. This is because the formation of the adduct involves the coordination of the Me3N molecule with the boron atom, resulting in a change in the bonding environment around the boron atom.

In general, when a Lewis acid (BF3) interacts with a Lewis base (Me3N), the bond length between the acid and the base can be different from the bond length in the isolated acid or base molecule. The coordination of the Lewis base to the Lewis acid can lead to a change in the bond length due to the formation of a coordinate bond.

In the case of the Me3N-BF3 adduct, the coordination of the Me3N molecule with the boron atom can result in a longer or shorter B-F bond length compared to the B-F bond length in BF3.

Possible B-F Bond Length in Me3N-BF3 Adduct
The exact bond length of B-F in the Me3N-BF3 adduct cannot be determined without experimental data or calculations. However, it is generally expected that the bond length in the adduct may be different from the bond length in the isolated BF3 molecule.

It is possible that the coordination of the Me3N molecule to the boron atom could result in a longer B-F bond length if the Me3N molecule donates electron density to the boron atom, weakening the B-F bond. Conversely, it is also possible that the coordination could result in a shorter B-F bond length if the Me3N molecule accepts electron density from the boron atom, strengthening the B-F bond.

Conclusion
In summary, the bond length of B-F in the Me3N-BF3 adduct can be different from the bond length in BF3. Without experimental data or calculations, it is not possible to determine the exact bond length in the adduct. It could be greater than, smaller than, or equal to the 1.30Å bond length in BF3.