Spot the error; choose ‘‘No error’’ if none. Sentence: They would not have able to plan the details of the job, if you had not cooperated.

Introduction / Context:
The structure under test is the modal perfect passive/ability expression ‘‘would have been able to + verb.’’ Learners often omit ‘‘been’’ and write ‘‘have able,’’ which is ungrammatical.

Given Data / Assumptions:

• Conditional type: third conditional counterfactual (past) indicated by ‘‘would not have … if you had not …’’
• Target phrase: ‘‘have able to plan’’
• Main verb idea: ability to plan

Concept / Approach:
Use ‘‘be able to’’ to express ability when modal auxiliaries are restricted by tense. In perfect constructions, insert the past participle ‘‘been’’: ‘‘would have been able to plan.’’

Step-by-Step Solution:
Identify intended form: modal perfect of ‘‘be able to.’’Insert required participle: change ‘‘have able’’ → ‘‘have been able.’’Full correction: ‘‘They would not have been able to plan the details of the job if you had not cooperated.’’

Verification / Alternative check:
Compare with similar verbs: ‘‘would have been ready,’’ ‘‘would have been willing’’—all require ‘‘been’’ after ‘‘have’’ for the perfect of ‘‘be.’’

Why Other Options Are Wrong:
A, C, and D are fine within the third-conditional framework. Only B omits the crucial ‘‘been.’’

Common Pitfalls:
Dropping ‘‘been’’ in perfect tenses; mixing second and third conditionals.

Final Answer:
have able to plan