The Past Participle form of the irregular verb 'bind' is:
 a. binded
 b. bound
 c. binding
 d. bind

Hint: Past participle is a participle that typically expresses completed action and that is traditionally one of the principal parts of the verb. It can be used as an adjective as well.

Complete step by step solution: “Past participle” is defined by the Oxford Dictionary as “the form of a verb, typically ending in -ed in English, which is used in forming perfect and passive tenses and sometimes as an adjective.”
Many verbs have a past participle with –ed:
cried
talked
called

However, the word ‘bind’ is not a regular verb. It is an irregular verb, which is a verb in which the past participle is not formed by adding the usual -ed ending. Example- bear-bore.
Let us thus analyze the options given to us in this question:
Option (a.), 'binded', has an ending of -ed.
Therefore, option (a.) is incorrect as the given word ‘bind’ is not a regular verb and therefore it’s past participle will not end with -ed.

Option (b.), ‘bound', follows the rule of syntax for a past participle of an irregular verb. For example, ‘bore’ follows the syntax as well (irregular verb- bear).
Therefore, option (b.) is correct.

Option (c.), ‘binding', is a word in present tense.
Therefore, option (c.) is incorrect as we need the past participle form of ‘bind’.

Option (d.), ‘bind', is again, a word in present tense.
Therefore, option (d.) is incorrect as we need the past participle form of ‘bind’.

Note: In this question, you need to identify the tense of the given options first, and see whether they are in past or present tense. Then proceed after keeping in mind that you are looking for a past participle of an irregular verb.