True about asthma -a) Increasing incidence day by dayb) Allergic asthma common in older patientsc) Increase in IgE in idiosyncratic asthmad) Bronchoconstriction

**Core Concept**
Asthma is a chronic inflammatory disease of the airways characterized by **bronchial hyperresponsiveness** and **variable airflow obstruction**. The underlying pathophysiology involves **inflammation**, **airway remodeling**, and **smooth muscle contraction**.

**Why the Correct Answer is Right**
The correct answer, **d) Bronchoconstriction**, is a key feature of asthma, resulting from the contraction of **smooth muscle** surrounding the airways, leading to **narrowing of the airway lumen**. This is often triggered by **allergens**, **irritants**, or **inflammatory mediators**.

**Why Each Wrong Option is Incorrect**
**Option A:** Increasing incidence day by day - While asthma incidence may be rising, this statement is too broad and does not specifically relate to the pathophysiology or clinical features of asthma.
**Option B:** Allergic asthma common in older patients - Allergic asthma is more common in **children and young adults**, not older patients.
**Option C:** Increase in IgE in idiosyncratic asthma - Idiosyncratic asthma is not typically associated with **increased IgE levels**, which are more characteristic of **allergic asthma**.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **bronchoconstriction** in asthma can be reversed with **bronchodilators**, such as **beta-2 agonists**, which are a mainstay of asthma treatment.

**Correct Answer:** D. Bronchoconstriction