To form the present participle, drop the ending of the infinitive verb and then add . OA. -iendo to ar verbs and ando to -er and -ir verbs
OB. -ando to -ar and -ir verbs and -iendo to -er verbs
OC. ando to ar verbs and -iendo to -er and ir verbs
OD. lendo to ir verbs and -ando to -ar ander verbs