About gait and balance disorders, which of the following are true or false? a) The commonest cause for gait disorder is multiple infarcts b) Tropical spastic paraparesis related to the retrovirus HTLV-II c) Freezing of gait is common in progressive supranuclear palsy and multiple-system atrophy d) Frontal gait disorder is known as the "slipping clutch" syndrome e) Fragile X premutation has been associated with gait ataxia in older men