c
The bond angle in \(BF _3\) is \(120^{\circ}\) since \(B\) is \(sp ^2\) - hybridized. In \(PF _3, P\) is \(sp ^3\) - hybridized but the bond angle is little less that \(109^{\circ} .28\) (but far greater than \(90^{\circ}\) ) due to bond pair - Ione pair repulsion. In \(CIF _3, Cl\) is \(sp ^3 d\) hybridized. It has \(T\) - shape and hence the bond angle is around \(90^{\circ}\). Therefore the correct order of increasing bond angle is \(ClF _3\,< \,PF _3\,<\, BF _3\)