Past Participle of Verbs

 The past participle of lay is lain. Hence, option 4 is correct.

 Had to is correct as it is the past participle of must.

The verb 'shear' has two acceptable past participle forms: 'sheared' (regular formation) and 'shorn' (irregular formation). Both are grammatically correct and used in different contexts - 'sheared' is more common when referring to cutting wool, while 'shorn' is typically used in poetic or literary contexts.

The past participle of 'slay' is 'slain' (the verb forms are: slay-slew-slain). This is an irregular verb that follows the pattern of i-a-u vowel gradation. 'Slayed' is incorrect, and 'slay' is the base form, not the past participle.

The past participle of 'hew' is 'hewn' (verb forms: hew-hewed-hewn). Option B 'hewed' is the simple past tense, not the past participle. The past participle is formed with the -en suffix typical of some irregular verbs like 'sow-sown' or 'mow-mown'.

The verb 'come' is irregular in that its past participle is identical to its base form: 'come' (verb forms: come-came-come). The past form 'came' is not used as the past participle. This is similar to other verbs like 'become-became-become' and 'run-ran-run'.

The verb 'set' is irregular in that all three forms are identical: 'set' (verb forms: set-set-set). No -ed suffix is added for any form. This is similar to other verbs like 'put-put-put', 'cut-cut-cut', and 'hit-hit-hit' which don't change form at all.

 The past participle is shorn.

The verb 'broadcast' (when written as one word) is irregular in that all three forms are identical: 'broadcast' (verb forms: broadcast-broadcast-broadcast). No -ed suffix is added for any form. This is similar to verbs like 'set-set-set' or 'put-put-put'. Note: The option is misspelled with a space ('broad cast') but this is the intended correct answer.

The past participle of 'slay' is 'slain' (verb forms: slay-slew-slain). This is an irregular verb that doesn't take the -ed suffix. 'Slayed' is grammatically incorrect, and 'slay' is the base form, not the past participle. The correct answer is 'slain'.

Overcome is an irregular verb that keeps the same form for past participle as the base form. Option B 'overcame' is the simple past form, not the past participle. Options C and D are incorrect conjugations.

Swim is an irregular verb: swim-swam-swum. The past participle is 'swum'. Option B 'swimmed' is an incorrect regularization. Option C is the base form.

Tread is an irregular verb: tread-trod-trodden. 'Trodden' is the past participle form. Option A 'trod' is the simple past form, not the past participle.

Shed is an irregular verb that keeps the same form for past participle. The base, past, and past participle are all 'shed'. Option A 'shedded' is an incorrect regularization.

Beget is an irregular verb: beget-begat-begotten. 'Begotten' is the past participle form. Options A, B, and D are incorrect conjugations.

Cost is an irregular verb that keeps the same form for past participle. The past participle of cost is 'cost', not 'costed'. In the meaning of estimating price, 'costed' can be used, but for the standard meaning of the verb, 'cost' is correct.

Cleave has two different meanings with different past participle forms. For 'to split apart', the forms are 'cleft' and 'cleaved' (past). For 'to adhere/stick together', the past participle is 'cloven'. Both 'cleft' and 'cloven' are correct depending on meaning.

Lead is an irregular verb: lead-led-led. The past participle is 'led'. Option A 'lead' (pronounced 'led') is the metal, not the verb form. Option B 'leaded' is only used for the metal-coating meaning, not the verb 'to guide'.

Let is an irregular verb that keeps the same form for past participle. The base, past, and past participle are all 'let'. Option B 'letting' is the present participle/gerund form, not the past participle.

The verb 'dare' is a regular verb, so its past participle is formed by adding '-ed' to create 'dared'. In perfect tenses, we use 'have/has/had dared' (e.g., 'She has dared to challenge them'). This follows the standard conjugation pattern for regular verbs.

The verb 'to be' is highly irregular and its past participle is 'been'. In perfect tenses, we use 'have/has/had been' (e.g., 'She has been working here for years'). 'Am', 'is', and 'was' are present and past tense forms, not the past participle needed for perfect constructions.