$\begin {array} {1 1} (a)\;\overrightarrow F\: and\: \overrightarrow V \: are \: always\: perpendicular\: to\: each\: other \\ (b)\;\overrightarrow B\: and\: \overrightarrow V \: are \: always\: perpendicular\: to\: each\: other \\ (c)\;\overrightarrow F\: and\: \overrightarrow B \: are \: always\: perpendicular\: to\: each\: other \\ (d)\;\overrightarrow F\: is \: always\: perpendicular\: to\: both\: \overrightarrow B\: and \: \overrightarrow V \end {array}$