In this idiom based vocabulary question, choose the alternative that best expresses the meaning of the phrase “learn by heart”, as used when teachers ask students to fully master a poem or a formula.

Introduction / Context:
The idiom learn by heart is widely used in schools, colleges, and exam preparation. Teachers often ask students to learn poems, formulas, definitions, or speeches by heart before a test or performance. This question evaluates whether the learner understands the idiomatic meaning, which is different from the literal idea of the human heart. A solid grasp of this expression helps in following academic instructions and in understanding English texts that talk about memorisation and study habits.

Given Data / Assumptions:
Key points in the question are as follows:

• The idiom given is learn by heart.
• We need a meaning that fits common educational usage.
• The options mention memorising, making mistakes, loving something, and hiding feelings.
• We assume a general English learning context, especially exam preparation.

Concept / Approach:
Idioms usually carry figurative meanings that are well established. Learn by heart does not refer to any medical or emotional feature of the heart. Instead, it is a traditional way to say memorise something perfectly, so that you can recite or reproduce it without looking. The heart is used symbolically to represent complete internalisation. Therefore, the correct option must clearly express full memorisation rather than emotional love, painful experience, or suppression of feelings.

Step-by-Step Solution:
Step 1: Recall that learn by heart is commonly used by teachers in the sense of memorise completely. Step 2: Examine option a, which states that it means to memorize something so completely that you can recall it accurately. This matches the standard meaning very well. Step 3: Look at option b, which talks about learning a lesson after a painful mistake. That idea is closer to learning the hard way, not learn by heart. Step 4: Evaluate option c, which refers to loving something deeply and emotionally. That focuses on feelings rather than memorisation. Step 5: Consider option d, which speaks of learning to hide or suppress true feelings. This is related to emotional control, not the idiom asked in the question. Step 6: Conclude that option a is the only choice that correctly describes the idiom.

Verification / Alternative check:
To verify, imagine a teacher saying, You must learn this poem by heart for the recital tomorrow. No one would interpret this as loving the poem or hiding feelings. The natural interpretation is that students must memorise every line. If you compare this practical usage with each option, only option a fits. The others either deal with emotions or consequences of mistakes, which are unrelated to this idiom in standard English.

Why Other Options Are Wrong:
Option b is wrong because learning through a painful mistake is a different expression, often described as learning the hard way. Option c is incorrect since emotional love is not the main idea here, even though the word heart could suggest emotions. Option d is also wrong because hiding true feelings is about emotional self control, not memorising information. None of these capture the academic and memory based sense of learn by heart.

Common Pitfalls:
A regular confusion arises because learners associate the word heart only with emotions. This can mislead them into choosing meanings linked to love or feelings. Another pitfall is not paying attention to how the phrase appears in school contexts, where it is always connected with study and memorisation. To avoid such errors, learners should remember that many idioms use body parts metaphorically and their meanings must be learned as fixed phrases, not interpreted literally.

Final Answer:
The idiom learn by heart means to memorize something so completely that you can recall it accurately, which is correctly captured by option a.