<s>[INST] context: Physical features can vary depending on the type. It forms the basis for Sillence classification.
Type I: Osteogenesis imperfecta
This is the most common and mildest form. In subtype A, dentinogenesis imperfecta is absent, while in subtype B, dentinogenesis imperfecta is present. Symptoms of both subtypes include blue sclera, in utero fractures in 10% of patients (fractures are more common during infancy), mild-to-moderate bone fragility with frequency of fractures decreasing after puberty, kyphoscoliosis, hearing loss, easy
bruising and short stature.
Type II: Osteogenesis imperfecta
Osteogenesis imperfecta type II exhibits extreme bone fragility and frequent fractures. In utero fractures are present in 100% of cases. Many are stillborn, and 90% die before four weeks of age. Blue sclera may be present. Hearing loss is not common to type II OI. Dentinogenesis imperfecta may be present along with small nose, micrognathia and short trunk.
Type III: Osteogenesis imperfecta
Type III is associated with dentinogenesis imperfecta, sclera of variable hue, limb shortening and progressive deformities, triangular facies with frontal bossing and pulmonary hypertension. In utero fractures occur in 50% of cases. The remaining half of the cases have fractures in the neonatal period. No hearing loss has been reported in this type.
Type IV: Osteogenesis imperfecta
In subtype A, dentinogenesis imperfecta is absent, while in subtype B, dentinogenesis imperfecta is present. Symptoms of both subtypes include normal sclera, normal hearing, fractures that begin in infancy (in utero fractures are rare) and mild angulation and shortening of long bones. Bleeding diathesis have not been reported in this type. [/INST] question: According to Sillence classification of osteogenesis imperfecta, most common and mildest form is: | options: A: Type 1 B: Type 2 C: Type 3 D: Type 4 | answer: A </s>